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Whether you’re following the new textbook or revising for your final term, this Chemistry Class 9 Guess Paper 2026 by Inam Jazbi highlights the most expected questions, repeated concepts, and key topics every student must prepare.
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✅ 100% important MCQs, short & long questions
✅ Based on new paper pattern 2026
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IX Chemistry Important MCQs of Text
X Chemistry MCQs for Board Paper 2026
IX & XII Valency
IX Conceptual Chemistry Book by Dr. Inam
IX Model Test Questions (Chemistry Test)
IX Model Test Questions Class 9
Fundamentals of Chemistry
IX Chemistry Model Test Questions
✏️ IX-CHEMISTRY Guess Paper 2026 with solution
Dr Inam Ul Haq Jazbi ✏️
✏️ Section-B (Short-Answer Questions) 8 Questions 3 marks each (24) ✏️
Valency, Electronegativity, electron affinity, Tyndall effect, relative atomic mass, formula mass, free radical, molecular ion, mole, molar volume, empirical and molecular formula, Molarity, Solubility, concentration, false solution, mass/volume percent, Freezing Point, alloy, heterogenous mixture, absolute zero, allotropy, Dobereiner’s law of Triads, Newland’s law of Octaves, Mendeleev’s Periodic law, Periodicity, periodic trend, modern, periodic law, electronegativity, electrolysis.
OR
What do you mean by chemical species? Explain ion, molecular ion and free radical with examples.
(i) Alkali metal and halogens
(ii) Ionic, covalent bond and dative bond
(iii) Elements, compounds and mixtures
(iv) Ionic compounds and covalent compounds
(v) Solution, suspension and Colloid
(vi) Metal, metals and metalloids
(vii) Atom and molecule and ion
(viii) Molecule, molecular ion and free radical
(ix) Alkali metals and alkaline earths
(x) Cation and anion
(xi) Ion and free radical
(i) That chlorofluoro compounds are responsible for depletion of ozone layer.
(ii) That investigates the properties of ammonia gas.
(iii) That find out the quantity and quality of paracetamol in Panadol tablet.
OR
What is chemistry? Define its main branches briefly. What are green chemistry and environmental chemistry. Discuss how they are helpful in reducing pollution?
OR
What is meant by atomic number and mass number? Define and give uses of isotopes. Discuss the isotopes of Hydrogen or carbon or uranium. Mention the number of electrons, protons & neutrons in following atoms:
¹⁴₆C, ¹⁸₈O, ²³⁵₉₂U, ²⁴₁₂Mg²⁺, ³⁷₁₇Cl⁻, ²⁷₁₃Al³⁺
Differentiate between empirical and molecular formula. Describe relationship between empirical and molecular formula?
Empirical formula: It shows the simplest whole number ratio of atoms in a compound.
Molecular formula: It shows the actual number of atoms of each element in a molecule.
Relationship:
Molecular formula = n × Empirical formula
Where n is an integer calculated by:
n = Molecular mass / Empirical formula mass
Example:
Empirical formula = CH₂O
Empirical formula mass = 12 + 2×1 + 16 = 30 amu
Molecular mass = 60 amu
n = 60 / 30 = 2
Molecular formula = (CH₂O) × 2 = C₂H₄O₂
Complete the following chart:
| Compound | Molecular formula | Integer (n) | Empirical formula |
|---|---|---|---|
| Ethene | C₂H₄ | 2 | CH₂ |
| Hydrogen peroxide | H₂O₂ | 2 | HO |
| Glucose | C₆H₁₂O₆ | 6 | CH₂O |
(i) 3Li or 8O or 15P
(ii) 9F or 11Na and 17Cl
(iii) 12Mg or 13Al or 14Si
OR
An element has 7 (or 1 or 2 or 8) electrons in its M-shell. Answer the following questions:
(i) Determine its atomic number and give its Electronic configuration.
(ii) Identify the group, period and block of given element.
(iii) Write down three characteristics of the belonging group. Also write down the name and symbol of radioactive element of this group.
OR
Define symbol. How is symbol of an element written? Write down names and symbols of element starting with C, S, N, O and B.
OR
Draw the electronic dot and cross structures for H₂, N₂, O₂, CH₄, NH₃ and C₂H₂.
Sand (SiO₂), Limestone (CaCO₃), Sodium nitrate (NaNO₃), table salt (NaCl), sal ammoniac (NH₄Cl), Caustic soda (NaOH), caustic potash (KOH), washing soda (Na₂CO₃·10H₂O), baking soda (NaHCO₃), soda ash (Na₂CO₃), Epsom salt (MgSO₄·7H₂O), gypsum (CaSO₄·2H₂O), oleum (H₂S₂O₇), marsh gas (CH₄), blue vitriol (CuSO₄·5H₂O), sugar (C₁₂H₂₂O₁₁), ethyl alcohol, Acetylene, Ethylene.
OR
What is coordinate covalent bond? Explain with two examples.
OR
Define metallic bond. How are metallic bonds formed?
OR
Describe wave particle duality of electron of De Broglie Hypothesis? Prove that modern theory of De Broglie is related with Einstein and Plank's equations.
OR
Give three properties of canal rays.
OR
Justify that Rutherford atomic model has defects? What are Limitations of Bohr's Atomic Model?
OR
What is shielding effect? Explain how shielding effect influence the periodic trends?
2KClO₃ → 2KCl + 3O₂
2Ba(NO₃)₂ → 2BaO + 4NO₂ + O₂
2Na + 2H₂O → 2NaOH + H₂
2NH₃ + 3Cl₂ → N₂ + 6HCl
MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
4NH₃ + 5O₂ → 4NO + 6H₂O
4Zn + 10HNO₃ → 3H₂O + NH₄NO₃ + 4Zn(NO₃)₂
3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O
2KNO₃ → 2KNO₂ + O₂
Ca + 2H₂O → Ca(OH)₂ + H₂
2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O
OR
How is electronegative value determined in the formation of chemical bond? Describe ionic character in covalent bond.
OR
What is meant by bond pair, lone pair and unpaired electrons? How many unpaired electrons are there in oxygen atom and nitrogen atom? How many lone pairs are there in nitrogen molecule and oxygen molecule?
OR
What is diffusion and Graham’s law of diffusion of gases? Which gas from among CO₂, CH₄ and NH₃ will diffuse the fastest and why? Give the reason.
OR
Define ionization energy or electron affinity. Describe trend in group and period with examples of any one of them.
OR
Explain the solute-solvent interaction to prepare sodium chloride solution.
Zn + Cl₂ → ZnCl₂
OR
Differentiate between electrolytes and non-electrolytes with examples. Identify strong and weak electrolytes from the following:
HCl (S), KI (S), NaOH (S), H₂S (W), CH₃COOH (W), NH₄OH (W), NaCl (S), C₂H₅OH (W)
OR
Write down the composition of following alloys:
Brass (Cu-Zn,[4:1]), Bronze (Cu-Sn-Zn) [9:1], Bell metal (Cu-Sn), Monel (Ni-Cu-Fe), Amalgam (Hg-Ag-Cu-Zn), Pewter (Sn-Cu-Pb-Sb-Bi), White gold (Au-Pb-Ag-Cu (18 karat)), Duralumin (Al-Cu-Mg-Ni)
OR
Write names and symbols of some noble metals. Explain inertness of noble metals with their importance.
OR
Define Moh Scale. What are Soft & Hard Metals? Differentiate between sodium and iron as soft and hard metal.
OR
Differentiate between metal and metals. Identify the elements as metals, non-metals and metalloids from the following:
C, Ca, Sb, S, Sr, Se, K, P, N, Ba, Ge, I, Al, B, As
OR
What is plasma? Explain plasma with the daily life examples?
OR
Explain importance of Silver and gold.
(i) Why gasoline does not dissolve in water?
(ii) Alkali metals are not found in free state in nature, why?
(iii) Why ionic compounds conduct electricity in molten or in aqueous solutions only?
(iv) Why the solubility of a salt increases with the increase in temperature?
(v) Explain why table salt has a very high melting point.
(vi) Atomic radii increase down a group and decrease across a period.
(vii) Alkali metals have the largest while halogens have the smallest atomic radii in their period.
(viii) Shielding effect of inner electrons remains the same across a period.
(ix) Ionization energy, electron affinity and electronegativity show same trends across a period.
(x) Covalent bonds are strong and hard to break but why most of the covalent compounds have low melting and boiling points.
(xi) Why the rate of diffusion of gases is rapid than that of liquids?
(xii) How does electron differ from proton or neutron?
(xiii) Helium diffuses faster than methane.
✏️ Section-C (Long-Answer Questions) 4 Questions 6 marks each ✏️
OR
Determine the demarcation of periodic table into s, p, d and f blocks.
OR
State modern periodic law. Explain periods in the modern periodic table.
OR
Write down 6 postulates of Bohr’s atomic model.
OR
What is meant by covalent bond and coordinate covalent bond? Describe the formation of a covalent bond between two nonmetallic atoms. Explain single, double and triple covalent bond with examples. Explain dative bond with two examples.
OR
Define vapour pressure. How equilibrium state involved in vapour pressure of liquids in close system? Describe the factors which affect on vapour pressure.
OR
Discuss discharge tube experiment for the discovery of electrons with 4 properties of cathode rays.
OR
Explain the importance of glues and epoxy resins in our society.
OR
What is electroplating? How steel object can be electroplated with zinc, tin and silver?
OR
What are transition elements? Give their types. Give their 4 general properties.
OR
What is allotropy? Describe different allotropes of carbon.
OR
Describe the construction and working of lead battery or dry cell.
OR
What are mixtures? Give its examples. Discuss its two types with examples.
✏️ Numericals✏️
OR
Calculate the number of moles, number of molecules and number of atoms present in 10 g of H₂SO₄.
OR
What is the molarity of the solution prepared by dissolving 1.25 g of HCl gas into enough water to make 30 cm³ of solution?
OR
A solution of 20 cm³ of alcohol is dissolved in 80 cm³ of water. Calculate the concentration (v/v) of solution.
OR
A sample of sulphuric acid has the molarity 20M. How many cm³ of solution should you use to prepare 500 cm³ of 0.5M H₂SO₄?
OR
A sample of Hydrogen gas has a volume of 350 cm³ at 40°C. If gas is allowed to expand up to 700 cm³ at constant pressure. Find out its final temperature?
✏️ Important MCQs for Class 9 Chemistry Paper ✏️
✏️ Smart Answers of Section-B (Short-Answer Questions) ✏️
Q1. Define any three of the following
Valency is the combining capacity of an atom, i.e., the number of electrons it can lose, gain, or share during chemical bonding.
Electronegativity is the tendency of an atom to attract the shared pair of electrons towards itself in a chemical bond.
Electron affinity is the energy released when a neutral atom gains an electron to form a negative ion.
The scattering of light by colloidal particles when a beam of light passes through them is called the Tyndall effect.
Relative atomic mass is the average mass of an atom compared with one-twelfth of the mass of a carbon-12 atom.
Formula mass is the sum of the atomic masses of all the atoms present in one formula unit of a compound.
A free radical is an atom or group of atoms containing an unpaired electron and is therefore highly reactive.
A molecular ion is a charged molecule formed by the loss or gain of one or more electrons without fragmentation.
A mole is the amount of substance that contains 6.022 × 1023 particles (Avogadro’s number).
Molar volume is the volume occupied by one mole of a gas at STP, equal to 22.4 dm3.
Empirical formula shows the simplest whole-number ratio of atoms of different elements in a compound.
Molecular formula shows the actual number of atoms of each element present in one molecule of a compound.
Molarity is the number of moles of solute dissolved per liter of solution.
Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.
Concentration is the amount of solute present in a given quantity of solution.
A false solution is a colloidal system that appears homogeneous but is actually heterogeneous.
Freezing point is the temperature at which a liquid changes into a solid and both phases coexist in equilibrium.
An alloy is a homogeneous mixture of two or more metals or a metal with a non-metal.
A heterogeneous mixture has a non-uniform composition and visibly different phases.
Absolute zero is the lowest possible temperature (0 K or −273 °C) at which molecular motion stops.
Allotropy is the property of an element to exist in different physical forms in the same state.
Electrolysis is the chemical decomposition of a compound by passing an electric current through it.
OR
What do you mean by chemical species? Explain ion, molecular ion and free radical with examples.
A chemical species is any atom, molecule, ion, or group of particles that has a definite chemical identity and can take part in a chemical reaction ⚛️.
An ion is an atom or molecule that carries an electric charge due to loss or gain of electrons.
Positive ion (cation): formed by loss of electrons ➕
Example: Na+
Negative ion (anion): formed by gain of electrons ➖
Example: Cl−
A molecular ion is a charged species formed when a molecule gains or loses electrons without breaking apart.
Usually formed in mass spectrometry by loss/gain of electrons without fragmentation.
Examples: H2+, O2+, N2+
👉 These ions keep the original molecule intact; only the charge changes.
A free radical is an atom or group of atoms that contains an unpaired electron, making it highly reactive ⚠️.
Examples: CH3• (methyl radical), Cl•
2. Write down three differences between any one of the following:
(i) Alkali metal and halogens
(ii) Ionic, covalent bond and dative bond
(iii) Elements, compounds and mixtures
(iv) Ionic compounds and covalent compounds
(v) Solution, suspension and Colloid
(vi) Metal, metals and metalloids
Answer
Distinction between Ionic and Covalent Compounds
Difference between Solution, Suspension and Colloids
Difference between Metals, Non-metals and Metalloids
Difference between Alkali Metals and Halogens
Difference between Ionic, Covalent and Dative Bond
| S. # | Ionic Bond | Covalent Bond | Dative Covalent Bond |
|---|---|---|---|
| 1 | Complete transference of electrons | Mutual sharing of electrons | One-sided sharing of electrons |
| 2 | Electrostatic attraction between ions | Attraction between electrons & nuclei | Attraction between lone pair & nuclei |
| 3 | Atom loses electron → cation; other gains → anion | Atoms share equal electrons | One atom donates pair, other accepts |
| 4 | E.N. difference > 1.7 | E.N. difference < 1.7 | One atom has lone pair, other has sixtet |
| 5 | Polar bond | May be polar or non-polar | Semi-polar bond |
| 6 | Always single bond | Single, double, or triple | Always single bond |
| 7 | Non-directional | Directional | Directional |
Difference between Elements, Compounds and Mixtures
| Elements | Compounds | Mixtures |
|---|---|---|
| Element is a substance made up of same atoms and discovered naturally | Compound is a substance formed by chemical combination of atoms of the elements | Mixture is an impure substance formed by the simple mixing of substances |
| Element shows unique properties due to similarity of atoms; same atomic number | Constituents lose their identity and form a new substance with new properties | Constituents retain their properties in mixture; no fixed composition |
| Cannot decompose into simpler substances by ordinary means | Cannot be separated by physical means | Can be separated by physical means |
| Represented by symbols; homogeneous | Represented by chemical formula; homogeneous composition | No chemical formula; may be homogeneous or heterogeneous |
| Melting point increases with atomic number | Compounds have sharp and fixed melting points | Mixtures do not have sharp and fixed melting points |
Q3. What is chemistry? Define its main branches briefly. What are green chemistry and environmental chemistry. Discuss how they are helpful in reducing pollution?
🔬 What is Chemistry?
Chemistry is the study of matter, its composition, properties, and the changes it undergoes.
📚 Main Branches
• ⚗️ Organic Chemistry: Study of carbon compounds.
• 🧪 Inorganic Chemistry: Study of minerals, salts, metals.
• 🔬 Physical Chemistry: Energy, thermodynamics, kinetics.
• 💊 Biochemistry: Chemical processes in living organisms.
• 🧮 Analytical Chemistry: Identification and analysis of substances.
🌱 Green Chemistry
Focuses on designing eco‑friendly processes and products that minimize waste and avoid harmful chemicals.
🌍 Environmental Chemistry
Studies chemical processes in air, water, and soil, and their impact on ecosystems and human health.
✨ Role in Reducing Pollution
✅ Green chemistry reduces toxic by‑products and promotes sustainable alternatives.
✅ Environmental chemistry monitors pollutants and helps in developing strategies to control them.
Together, they protect nature and improve quality of life.
OR Q3. The following statements belong to which branch of chemistry? Identify:
(i) That chlorofluoro compounds are responsible for depletion of ozone layer.
(ii) That investigates the properties of ammonia gas.
(iii) That find out the quantity and quality of paracetamol in Panadol tablet.
📘 Answer
(i) 🌍 Environmental Chemistry
(ii) ⚗️ Inorganic Chemistry
(iii) 🧪 Analytical Chemistry
Q3. What is meant by atomic number and mass number. Define and give uses of isotopes. Discuss the isotopes of Hydrogen or carbon or uranium. Mention the number of electrons, protons and neutrons in following atoms:![]()
The number of protons present in the nucleus of an atom of an element is called the atomic number.
The sum of the number of protons and neutrons of an atom is called mass number.
Atoms of the same element having same atomic number (same number of protons & electrons) but different mass numbers (different number of neutrons).
Different isotopes show same chemical properties but different physical properties.
| S # | Radioactive Isotope | Field | Uses |
|---|---|---|---|
| 1 | Phosphorus-32 | Radiotherapy | Treatment of skin cancer |
| 2 | Strontium-90 | Radiotherapy | Treatment of bone cancer |
| 3 | Cobalt-60 | Radiotherapy | Treatment of internal cancers (penetrating power) |
| 4 | Iodine-131 | Radiotherapy | Detection of thyroid gland disorders |
| 5 | Technetium | Radiotherapy | To monitor the bond growth in fracture healing |
| 6 | Carbon-14 | Archaeology / Geology | Dating fossils and archaeological specimens |
| 7 | Uranium-235 | Power generation | Conversion of water energy from steam to generate electricity |
| 8 | Plutonium-238 | Medicine | Used to stimulate a regular heart beat in heart pace maker |
| 9 | Gamma rays of cobalt-60 | Medical instrumentation | For sterilization of medical instruments and dressings from harmful bacteria |
| 10 | Americium-231 | Safety measures and industries | Used in back scatter gauges, smoke detectors, fill height detectors and measuring ash content of coal |
| 11 | Gold-198 and technetium-99 | Sewage & liquid movement for water pollution | Tracing factory waste causing ocean pollution Tracing sand movement in rivers and oceans |
| Property | Symbol | Atomic No | Mass No | Protons | Electrons | Neutrons | % Abundance |
|---|---|---|---|---|---|---|---|
| Protium | ₁¹H | 1 | 1 | 1 | 1 | 0 | 99.985% |
| Deuterium | ₁²H | 1 | 2 | 1 | 1 | 1 | 0.0156% |
| Tritium | ₁³H | 1 | 3 | 1 | 1 | 2 | 4×10⁻¹⁵ % |
There are two stable isotopes and one radioactive isotope of carbon. Carbon-12 contains 6 protons and 6 neutrons, Carbon-13 has 6 protons and 7 neutrons, and Carbon-14 contains 6 protons and 8 neutrons. Carbon-12 is the most abundant (98.889%).
| Property | Symbol | Atomic No | Mass No | Protons | Electrons | Neutrons | % Abundance |
|---|---|---|---|---|---|---|---|
| Carbon-12 | ₆¹²C | 6 | 12 | 6 | 6 | 6 | 98.889% |
| Carbon-13 | ₆¹³C | 6 | 13 | 6 | 6 | 7 | 1.111% |
| Carbon-14 | ₆¹⁴C | 6 | 14 | 6 | 6 | 8 | — |
There are three common isotopes of uranium with atomic number 92 and mass numbers 234, 235, and 238. Uranium is found 99% in nature.
| Property | Symbol | Atomic No | Mass No | Protons | Electrons | Neutrons | % Abundance |
|---|---|---|---|---|---|---|---|
| Uranium-234 | ₉₂²³⁴U | 92 | 234 | 92 | 92 | 142 | 0.0055% |
| Uranium-235 | ₉₂²³⁵U | 92 | 235 | 92 | 92 | 143 | 0.7200% |
| Uranium-238 | ₉₂²³⁸U | 92 | 238 | 92 | 92 | 146 | 99.2745% |
Calculation of Number of Protons, electrons and neutrons
146C, 188O, 23592U, 2412Mg2+, 3717Cl-, 2713Al3+
| No of Protons (Z) | No of electrons (Z or Z ± charge) | No of neutrons (A – Z) | |
|---|---|---|---|
| 146C | 6 | 6 | 14 – 6 = 8 |
| 188O | 8 | 8 | 18 – 8 = 10 |
| 23592U | 92 | 92 | 235 – 92 = 143 |
| 2412Mg2+ | 12 | 12 – 2 = 10 | 24 – 12 = 12 |
| 3717Cl- | 17 | 17 + 1 = 18 | 37 – 17 = 20 |
| 2713Al3+ | 13 | 13 – 3 = 10 | 27 – 13 = 14 |
OR
Differentiate between EF and MF. Describe relationship between empirical and molecular formula? Find out molecular formula of a compound if its empirical formula is CH₂O and molecular mass 60 amu. Complete the following chart:
📘 Difference between Empirical Formula and Molecular Formula
🔗 Relationship Between EF and MF
The empirical formula may or may not be the same as the molecular formula. They are the same only when the simplest and actual atomic ratios are identical.
Ionic compounds like NaCl, MgCl₂, MgO often have same EF and MF.
Molecular Formula = (Empirical Formula)ₙ
Where n is a whole number (1, 2, 3...). If n = 1, then EF = MF.
🧮 Find Out Molecular Formula
Empirical formula = CH₂O
Molecular mass = 60 amu
EF mass = 12 + 2×1 + 16 = 30 amu
n = 60 ÷ 30 = 2
Molecular Formula = (CH₂O)₂ = C₂H₄O₂
📊 Completed Chart
Q4. Define symbol. How is symbol of an element written? Write down names and symbols of element starting with C, S, N, O and B
📘 Definition
A symbol is a shorthand notation used to represent an element in chemistry.
✍️ Writing of Symbols
• First letter always capital.
• Second letter (if any) always small.
Example: Carbon → C, Sodium → Na.
🔠 Examples
• 🌿 Carbon → C
• 🌍 Sulphur → S
• 🌬️ Nitrogen → N
• 💨 Oxygen → O
• 🔹 Boron → B
OR
Q4. Identify group and period in the periodic table of the following elements:
(i) ₃Li or ₁₅P
(ii) ₉F and ₁₇Cl
(iii) ₁₂Mg or ₁₃Al or ₁₄Si
OR
An element has 7 (or 1 or 2 or 8) electrons in its M-shell. Answer the following questions:
(i) Determine its atomic number and give its Electronic configuration.
(ii) Identify the group, period and block of given element.
(iii) Write down three characteristics of the belonging group. Also Write down the name and symbol of radioactive element of this group.
📘 Answer
Element identification based on electronic configuration:
| Element with Z | Electronic Configuration | Group | Period | Block |
|---|---|---|---|---|
| ₃Li | 1s², 2s¹ | IA | 2 | s |
| ₁₅P | 1s², 2s² 2p⁶, 3s² 3p³ | VA | 3 | p |
| ₉F | 1s², 2s² 2p⁵ | VIIA | 2 | p |
| ₁₇Cl | 1s², 2s² 2p⁶, 3s² 3p⁵ | VIIA | 3 | p |
| ₁₂Mg | 1s², 2s² 2p⁶, 3s² | IIA | 3 | s |
| ₁₃Al | 1s², 2s² 2p⁶, 3s² 3p¹ | IIIA | 3 | p |
| ₁₄Si | 1s², 2s² 2p⁶, 3s² 3p² | IVA | 3 | p |
🧮 Finding out atomic number and EC
Z = 2ē in K + 8ē in L + 7ē in M = 17
EC = K², L⁸, M⁷ or 1s² 2s² 2p⁶, 3s² 3p⁵
🔗 Identifying the group, period and block
Group = VIIA
Period = 3
Block = p-block
📘 Characteristics of the belonging group
➡️Highly electronegative elements
➡️Have 7 valence electrons
➡️ns² np⁵ valence shell EC
➡️Forms univalent anions
➡️Acts as oxidizing agents
➡️Forms diatomic molecules
☢️ Radioactive element of this group
Astatine (At)
Q5. Draw the electronic dot and cross structures for H₂, N₂, O₂, CH₄, NH₃ and C₂H₂.
📘 Answer (Dot & Cross Structures)
• ⚪ H₂ → Single covalent bond (H–H)
• 🟣 N₂ → Triple bond (N≡N) with lone pairs
• 🔵 O₂ → Double bond (O=O) with two lone pairs each
• 🟢 CH₄ → Carbon bonded to 4 hydrogens (tetrahedral)
• 🟡 NH₃ → Nitrogen bonded to 3 hydrogens + one lone pair
• 🔺 C₂H₂ → Carbon–carbon triple bond (HC≡CH)
OR
Q5. Compare reactivity of Alkali and Alkaline Earth Metals
📘 Answer
| Alkali Metals (IA) | Alkaline Earth Metals (IIA) |
|---|---|
| More reactive, low I.E | Less reactive, high I.E |
| Form M⁺ ions | Form M²⁺ ions |
| Violent with halogens 2Na + Cl → 2NaCl |
Slow with halogens Ca + Cl₂ → CaCl₂ |
| Tarnish in air 2K + O₂ → K₂O₂ |
Oxides on heating 2Mg + O₂ → 2MgO |
| Vigorous with water 2K + 2H₂O → 2KOH + H₂ |
Slow with cold water Mg + H₂O → MgO + H₂ MgO + H₂O → Mg(OH)₂ |
| More basic oxides | Less basic oxides |
| No carbides | Form carbides Ca + 2C → CaC₂ |
OR
Write down one contribution of any 10 scientists in the field of chemistry.
📘 Answer
| English Scientist | Contribution |
|---|---|
| J. Priestly | Discovered oxygen, hydrogen chloride and sulphur dioxide. |
| Scheele | Discovered chlorine. |
| Cavendish | Discovered hydrogen. |
| Lavoisier | Discovered that oxygen constituted about 1/5th of air. |
| J.J. Berzelius | Introduced the idea of symbols, formulae & chemical equations. |
| Mendeleev | Published the periodic table or periodic arrangement of the elements. |
| Arrhenius | Put forward his ionic theory of ionization. |
| M. Faraday | Study of electromagnetism and electrochemistry, discovered the laws of electrolysis. |
| J.J. Thomson | Discovered electrons by experiments. |
| Henry Moseley | Discovered atomic number that led to the development of modern periodic table. |
OR
Explain the importance of glues and epoxy resins in our society.
📘 Answer
Synthetic adhesives like epoxy resins and glues are substances that bond surfaces together. Epoxy forms strong bonds with glass, plastics, plywood, ceramics, and laminated boards. It is widely used in decorative flooring and in places requiring water resistance such as bridges, dams, and power stations.
✈️ Use in Vehicles & Structures
Aircrafts, cars, trucks, and boats are partly held together with epoxy adhesives. Their excellent bonding strength comes from strong attraction between resin and substrate. Epoxy is a common construction adhesive in transport industries, with a quick drying time of 6–30 minutes.
Q6. Write chemical formulae of any three of the following compounds:
Sand (SiO₂), Limestone (CaCO₃), Sodium nitrate (NaNO₃), Table salt (NaCl),
Sal ammoniac (NH₄Cl), Caustic soda (NaOH), Caustic potash (KOH),
Washing soda (Na₂CO₃·10H₂O), Baking soda (NaHCO₃), Soda ash (Na₂CO₃),
Epsom salt (MgSO₄·7H₂O), Gypsum (CaSO₄·2H₂O), Oleum (H₂S₂O₇), Marsh gas (CH₄),
Blue vitriol (CuSO₄·5H₂O), Sugar (C₁₂H₂₂O₁₁), Ethyl alcohol, Acetylene, Ethylene.
📘 Answer
| Compound | Formula |
|---|---|
| Sand | SiO₂ |
| Limestone | CaCO₃ |
| Blue vitriol | CuSO₄·5H₂O |
| Washing soda | Na₂CO₃·10H₂O |
| Baking soda | NaHCO₃ |
| Soda ash | Na₂CO₃ |
| Epsom salt | MgSO₄·7H₂O |
| Gypsum | CaSO₄·2H₂O |
| Oleum | H₂S₂O₇ |
| Marsh gas | CH₄ |
| Ethyl alcohol | C₂H₅OH |
| Sugar | C₁₂H₂₂O₁₁ |
| Glucose | C₆H₁₂O₆ |
| Acetylene | C₂H₂ |
| Ethylene | C₂H₄ |
| Oil of vitriol | H₂SO₄ |
| Caustic soda | NaOH |
| Caustic potash | KOH |
OR
What is coordinate covalent bond? Explain with two examples.
📘 Definition
A coordinate covalent (dative) bond is a covalent bond in which both bonding electrons are donated by one atom. This concept was proposed by Sidgwick.
🔗 Example 1: Ammonium Chloride (NH₄Cl)
Ammonia donates its lone pair on nitrogen to H⁺ from HCl, forming NH₄⁺.
Equation:
NH₃ + HCl → NH₄Cl
🔗 Example 2: Hydronium Ion (H₃O⁺)
Water donates its lone pair on oxygen to H⁺, forming H₃O⁺.
Equation:
H₂O + H⁺ → H₃O⁺
OR
Define metallic bond. How are metallic bonds formed?
📘 Definition
A metallic bond is the force of attraction between positive metal ions and the sea of delocalized electrons around them.
⚙️ Formation
• Metal atoms release valence electrons.
• These electrons move freely, forming an “electron cloud”.
• Positive ions are held together by attraction to this cloud → strong metallic bonding.
• Explains properties like conductivity, malleability, and lustre.
Q7. Give three properties of canal rays.
📘 Answer
• 🌟 Canal rays consist of positively charged particles (protons).
• 💡 They travel in straight lines and produce a glow on striking a surface.
• ⚡ They are deflected by electric and magnetic fields, opposite to cathode rays.
OR
Q7. Write down any three points of atomic model proposed by Schrödinger or Bohr.
OR
Describe wave-particle duality of electron of De Broglie Hypothesis? Prove that modern theory of de Broglie is related with Einstein and Planck's equations.
📘 Schrödinger Atomic Model (1926)
Schrödinger introduced the quantum mechanical model using mathematical equations to describe electron positions.
Key Points:
1. Electrons exist as a fuzzy cloud around the nucleus; dense regions = orbitals.
2. Subshells have different shapes (s = spherical, p = dumbbell, etc.).
3. Orbitals are named s, p, d, f depending on energy and shape.
🔗 De Broglie Hypothesis (1923)
De Broglie proposed electrons and all matter show both particle and wave nature. Wavelength (λ) is given by: λ = h/p (where p = momentum). This duality applies to electrons, protons, neutrons, atoms, and molecules.
🧮 Proof Linking Einstein & Planck
Planck: E = hν
Einstein: E = mc²
Equating: hν = mc² → ν = c/λ
⇒ λ = h/mc
For moving particles: λ = h/mv (de Broglie’s equation).
Q8. Write down electronic configuration of ₅B, ₉F, ₇N, ₁₁Na, ₁₅P, ₂₀Ca, ₁₉K⁺, ₈O²⁻, ₁₆S²⁻, ₁₂Mg²⁺,₁₇Cl⁻.
OR
Justify that Rutherford atomic model has defects? What are Limitations of Bohr's Atomic Model?
📘 Electronic Configurations
| Element / Ion | Electrons | Configuration |
|---|---|---|
| Boron (₅B) | 5 | 1s² 2s² 2p¹ |
| Nitrogen (₇N) | 7 | 1s² 2s² 2p³ |
| Fluorine (₉F) | 9 | 1s² 2s² 2p⁵ |
| Sodium (₁₁Na) | 11 | 1s² 2s² 2p⁶ 3s¹ |
| Phosphorus (₁₅P) | 15 | 1s² 2s² 2p⁶ 3s² 3p³ |
| Calcium (₂₀Ca) | 20 | 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² |
| Potassium ion (₁₉K⁺) | 18(19–1) | 1s² 2s² 2p⁶ 3s² 3p⁶ |
| Magnesium ion (₁₂Mg²⁺) | 10(12–2) | 1s² 2s² 2p⁶ |
| Oxide ion (₈O²⁻) | 10(8 + 2) | 1s² 2s² 2p⁶ |
| Sulphide ion (₁₆S²⁻) | 18(16 + 2) | 1s² 2s² 2p⁶ 3s² 3p⁶ |
| Chloride ion (₁₇Cl⁻) | 18(17 + 1) | 1s² 2s² 2p⁶ 3s² 3p⁶ |
🔗 Defects in Rutherford’s Model
1. Could not explain atomic stability.
2. Classical physics predicts electrons lose energy and collapse into nucleus.
3. Should give continuous spectrum, but atoms show line spectra.
📘 Limitations of Bohr’s Model
1. Failed to explain Zeeman effect (magnetic field influence).
2. Failed to explain Stark effect (electric field influence).
3. Contradicts Heisenberg Uncertainty Principle.
4. Could not explain spectra of larger atoms.
5. Works only for single-electron species (H⁺, Li²⁺, B³⁺).
OR
What is shielding effect? Explain how shielding effect influence the periodic trends?
📘 Definition
🛡️ Shielding effect is the reduction of effective nuclear charge on outer electrons due to inner electrons blocking attraction.
⚙️ Influence on Periodic Trends
• 📉 Ionization energy: Decreases with stronger shielding.
• 📏 Atomic size: Increases as outer electrons feel less pull.
• ⚡ Electronegativity: Decreases because nucleus attracts outer electrons less strongly.
• 🔄 Explains variations across groups and periods in the periodic table.
Q9. Balance any three of the following chemical equations:
OR
How is electronegative value determined the formation of chemical bond?
Describe ionic character in covalent bond.
📘 Answer
1. 2KClO₃ → 2KCl + 3O₂
2. 2Ba(NO₃)₂ → 2BaO + 4NO₂ + O₂
3. 2Na + 2H₂O → 2NaOH + H₂
4. 2NH₃ + 3Cl₂ → 6HCl + N₂
5. MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
6. 4NH₃ + 5O₂ → 4NO + 6H₂O
7. 4Zn + 10HNO₃ → 3H₂O + NH₄NO₃ + 4Zn(NO₃)₂
📘 Prediction of Bond Type Using Electronegativity
Electronegativity difference (ΔE.N.) helps predict bond nature:
➡️ If ΔE.N. > 1.7 — bond is ionic
➡️ If ΔE.N. < 1.7 — bond is covalent
➡️ If ΔE.N. > 0.5 and < 1.7 — bond is polar covalent (partially ionic)
➡️ If ΔE.N. = 0 or < 0.5 — bond is non-polar covalent (pure covalent)
Examples:
Non-polar: H–H, O=O, N≡N, CH₄, Cl–Cl
Polar covalent: H–F, H–Cl, H–O–H
📘 Ionic Character in Covalent Bond
Polar covalent bonds have partial ionic character due to unequal sharing of electrons. Such molecules behave like dipoles and are not purely covalent.
OR
What is meant by bond pair, lone pair and unpaired electrons? How many unpaired electrons are there in oxygen atom and nitrogen atom? How many lone pairs are there in nitrogen molecule and oxygen molecule?
📘 Answer
• 🔹 Bond pair: Shared pair of electrons between atoms.
• 🔸 Lone pair: Non‑bonding pair of electrons on an atom.
• ⚪ Unpaired electron: Single electron not paired in orbital.
• 🌬️ Oxygen atom → 2 unpaired electrons.
• 🌿 Nitrogen atom → 3 unpaired electrons.
• 🧪 Nitrogen molecule (N₂) → 1 lone pair per atom (total 2).
• 💨 Oxygen molecule (O₂) → 2 lone pairs per atom (total 4).
Q10. What is KMT? Give its main postulates with respect to three states of matter.
📘 Definition
Kinetic Molecular Theory (KMT) was proposed by Boltzmann, Maxwell, and Kelvin. It explains the structure and behavior of solids, liquids, and gases. All matter is made of tiny particles in constant random motion with kinetic energy. State of matter depends on particle arrangement, motion, and intermolecular forces.
🌬️ Gaseous State
1. Molecules are far apart and have negligible volume.
2. Move randomly in straight lines until collision.
3. Collisions are elastic — no energy loss.
4. Pressure is due to wall collisions.
5. Weak attractive and repulsive forces.
💧 Liquid State
1. Molecules are randomly arranged but closer than gases.
2. Lower kinetic energy than gases.
3. Molecules move freely but not compressible.
4. No fixed shape — takes container’s shape.
5. Boiling point depends on external pressure.
🧊 Solid State
1. Molecules are tightly packed with strong attraction.
2. Cannot move freely — only vibrate in place.
3. Definite shape and volume.
4. Sharp melting point for pure solids.
📊 Comparison of Three States of Matter (KMT)
| S # | Gas | Liquid | Solid |
|---|---|---|---|
| 1. | Particles widely separated with large empty spaces. | Particles relatively close but not tightly packed. | Particles very close and tightly packed. |
| 2. | Random motion in all directions. | Random motion in all directions. | Regular arrangement, vibrational motion only. |
| 3. | Negligible intermolecular forces. | Greater forces than gases. | Strongest intermolecular forces. |
| 4. | Highest kinetic energy. | Less than gases. | Lowest kinetic energy. |
| 5. | Compressible. | Not easily compressible. | Not compressible. |
OR
What is diffusion and Graham’s law of diffusion of gases?
Which gas from among CO₂, CH₄ and NH₃ will diffuse the fastest and why? Give the reason.
📘 Diffusion
Diffusion is the spontaneous mixing of molecules from high to low concentration due to random motion. It leads to gradual mixing and formation of a homogeneous mixture.
🌬️ Why Gases Diffuse Rapidly
Gas molecules move freely and quickly, allowing rapid diffusion.
📘 Graham’s Law of Diffusion
Proposed by Thomas Graham (1846), it states:
“Rate of diffusion ∝ 1 / √(molar mass or density)”
Lighter gases diffuse faster than heavier ones under same conditions.
🔍 Which Gas Diffuses Fastest?
Among CO₂, CH₄ and NH₃:
NH₃ has the lowest molar mass → diffuses fastest
CO₂ has the highest molar mass → diffuses slowest
CH₄ is in between
Order of diffusion rate: CO₂ < CH₄ < NH₃
OR
Define ionization energy or electron affinity. Describe trend in group and period with examples of any one them.
📘 Definition
• ⚡ Ionization energy: Energy required to remove an electron from an atom.
• 🌟 Electron affinity: Energy released when an atom gains an electron.
📈 Trend in Period
• Ionization energy generally increases left → right due to stronger nuclear pull.
• Example: Li (low IE) vs Ne (high IE).
📉 Trend in Group
• Ionization energy decreases top → bottom due to shielding and larger size.
• Example: F (high IE) vs I (lower IE).
Q11. Differentiate between Amorphous and Crystalline Solids?
OR
Explain the solute–solvent interaction to prepare sodium chloride solution.
📊 Comparison of Solids
| Characteristic | Crystalline Solids | Amorphous Solids |
|---|---|---|
| Nature | True solids | Pseudo solids |
| Arrangement | Regular, ordered | Irregular, random |
| Shape | Definite geometrical | Irregular |
| Melting Point | Sharp, fixed | Gradual, over range |
| Cleavage | Smooth surfaces | Irregular surfaces |
📘 Solute–Solvent Interaction (NaCl in Water)
To dissolve a solute:
1. Break solute–solute bonds.
2. Break solvent–solvent bonds to create space.
3. Form strong solute–solvent attractions.
In NaCl solution, water molecules surround ions:
– Negative end attracts Na⁺
– Positive end attracts Cl⁻
These forces overcome ionic bonds, so NaCl dissolves quickly.
Q12. Define electrochemical reaction and redox reaction. Write down 2 differences between oxidation and reduction and oxidizing agent and reducing agent with examples. Identify oxidizing and reducing agents of the following chemical reaction:
Zn + Cl₂ → ZnCl₂
📘 Electrochemical Reaction
A reaction where chemical energy is converted to electrical energy or vice versa. Oxidation and reduction are electrochemical processes.
📘 Redox Reaction
A reaction involving both oxidation (loss of electrons) and reduction (gain of electrons) simultaneously.
🔗 Oxidation vs Reduction
| Oxidation | Reduction |
|---|---|
| Addition of oxygen 2Mg + O₂ → 2MgO |
Removal of oxygen ZnO + C → Zn + CO |
| Addition of hydrogen Cl₂ +H₂ → 2HCl |
Removal of hydrogen 4NH₃ + 3O₂ → 2N₂ + 6H₂O |
| Loss of electron by a substance /De-electronation M → Mⁿ⁺ + nē |
Gain of electron by a substance /Electronation Mⁿ⁺ + nē → M |
| Increase in oxidation number of a substance |
Decrease in oxidation number of a substance |
| Oxidized |
Reduced |
| Oxidation occurs in Reducing agents |
Reduction occurs in Oxidizing agents |
Becoming more positive |
Becoming more negative |
| Occurs at anode |
Occurs at cathode |
🔗 Oxidizing vs Reducing Agent
| Oxidizing Agent | Reducing Agent |
|---|---|
| Gains electrons | Loses electrons |
| It oxidizes other but itself reduces. | It reduces others but itself oxidizes. |
| Examples: All reactive non-metals like F₂, Cl₂, O₂ etc. | Examples: All metals like Na, Mg, Zn etc. |
🧮 Identification in Reaction
Zn (Reducing Agent, oxidized) + Cl₂ (Oxidizing Agent, reduced) → ZnCl₂
OR
Differentiate between electrolytes and non‑electrolytes with examples. Identify strong and weak electrolytes from the following:
HCl (S), KI (S), NaOH (S), H₂S (W), CH₃COOH (W), NH₄OH (W), NaCl (S), C₂H₅OH (W)
📊 Difference between Electrolytes and Non‑Electrolytes
| Characteristic | Electrolytes | Non‑Electrolytes |
|---|---|---|
| Ionization | Ionize/dissociate into positive & negative ions in water → conduct electricity | Do not ionize in water → no conduction |
| Conductivity | Good conductors | Insulators |
| Polarity | Polar compounds | Non‑polar compounds |
| Bond Type | Ionic bonds | Covalent bonds |
| Dissociation | Dissociate into ions | Do not dissociate |
| Examples | All acids, bases & salts (HCl, NaOH, NaCl) | Most organic compounds (sugar, glucose, urea, glycerine) |
📘 Identification of Strong & Weak Electrolytes
Strong Electrolytes: HCl, KI, NaOH, NaCl
Weak Electrolytes: H₂S, CH₃COOH, NH₄OH, C₂H₅OH
Q14. What is corrosion of metal and rusting? Name the methods which are used to protect metal from corrosion. How cathodic protection prevent metal from corrosion?
📘 Corrosion
Corrosion is the reaction of metals with oxygen and moisture forming porous oxides, exposing metal for further attack.
🧲 Rusting of Iron
Rusting is corrosion of iron, an electrochemical process producing Fe₂O₃·nH₂O (reddish‑brown rust).
Oxidation: Fe → Fe²⁺ + 2e⁻
Reduction: O₂ + 2H₂O + 4e⁻ → 4OH⁻
Rust spreads as Fe²⁺ reacts with oxygen and water.
🔧 Methods of Prevention
1. Alloying: Mixing with Cr/Ni forms stainless steel, resists corrosion.
2. Metallic Coating (Electroplating): Coating with Sn, Zn, Cr, Ni, Ag protects surface.
3. Cathodic Protection: Iron made cathode; active metals (Mg, Al) act as sacrificial anode, oxidize instead of iron.
4. Paint Coating: Paint blocks oxygen, moisture, and chemicals.
OR
Write down the composition of following alloys:
📘 Answer
| Alloy Name | Components | Applications |
|---|---|---|
| Brass | Cu–Zn (4:1) | Door knobs, hand rails, pipes |
| Bronze | Cu–Sn–Zn (9:1) | Coins, medals, tools |
| Bell Metal | Cu–Sn | Casting of bells |
| Monel | Ni–Cu–Fe | Corrosion‑resistant containers |
| Amalgam | Hg–Ag–Cu–Zn | Dental fillings |
| Pewter | Sn–Cu–Pb–Sb–Bi | Ornaments |
| White Gold (18K) | Au–Pb–Ag–Cu | Jewelry |
| Duralumin | Al–Cu–Mg–Ni | Boats, aircrafts |
| Alnico | Fe–Al–Ni–Co | Magnets in loudspeakers |
| Yellow Gold (22K) | 91.67% Au + Ag, Cu, Zn | Jewelry |
| Red Gold (18K) | 75% Au + Cu | Jewelry |
| White Gold (18K) | 75% Au + Cu, Ag | Jewelry |
Q14. What are metalloids? Write names and symbols of any 5 metalloids.
📘 Definition
Metalloids are elements showing properties of both metals and non‑metals. Their oxides are amphoteric and many act as semiconductors.
📘 Position in Periodic Table
Found along the staircase line between metals and non‑metals (B to At).
📊 Examples
| Element | Symbol | Group |
|---|---|---|
| Boron | B | IIIA |
| Silicon | Si | IVA |
| Arsenic | As | VA |
| Antimony | Sb | VA |
| Tellurium | Te | VIA |
OR
Write names and symbols of some noble metals. Explain inertness of noble metals.
📘 Noble Metals
Gold (Au), Silver (Ag), Platinum (Pt), Iridium (Ir), Osmium (Os), Rhodium (Rh), Ruthenium (Ru), Palladium (Pd).
🔍 Reason of Inertness
Noble metals are less electropositive, resist oxidation and corrosion. They remain shiny and stable, hence used in ornaments and coins.
OR
Define Moh Scale. What are Soft and Hard Metals? Differentiate between sodium and iron as soft and hard metal.
📘 Moh Scale
Hardness = resistance of a material to scratching. Moh Scale (1812, Frederich Mohs) ranges from 1 (softest) to 10 (hardest). Example: Lead pencil = 1, Diamond = 10.
🔧 Soft vs Hard Metals
• Soft metals: Easily scratched, weak metallic bonding (Na, K, Rb).
• Hard metals: Resist scratching, strong metallic bonding (Ni, Fe, W).
📊 Difference between Sodium & Iron
| S # | Sodium (Na) | Iron (Fe) |
|---|---|---|
| 1 | Soft metal, Group IA | Hard metal, Group VIIIB |
| 2 | Large atomic size | Smaller atomic size |
| 3 | Moh scale = 0.5 | Moh scale = 4.5 |
| 4 | Weak metallic bonding | Strong metallic bonding |
| 5 | Cut easily with knife | Hammered into sheets/wires |
| 6 | Low density (0.97 g/cm³) | High density (7.87 g/cm³) |
| 7 | Low melting (98°C), boiling (890°C) | High melting (1535°C), boiling (2450°C) |
OR
Differentiate between metal and non‑metals. Identify the elements as metals, non‑metals and metalloids from the following: C, Ca, Sb, S, Sr, Se, K, P, N, Ba, Ge, I, Al, B, As
📘 Difference
• ⚙️ Metals: Lustrous, malleable, ductile, good conductors of heat & electricity.
• 🌿 Non‑metals: Dull, brittle, poor conductors, form acidic oxides.
🔎 Classification of Given Elements
• ⚙️ Metals: Ca, Sr, K, Ba, Al
• 🌿 Non‑metals: C, S, P, N, Se, I
• 🔸 Metalloids: Sb, Ge, B, As
Q15. What is the boiling point? How boiling point is affected by different factors? How boiling point of a substance is affected by atmospheric pressure?
📘 Boiling Point
The temperature at which vapour pressure of a liquid equals atmospheric pressure is called its boiling point.
📊 Factors Affecting Boiling Point
1. Atmospheric Pressure: Higher pressure → higher boiling point. Example: pressure cooker.
2. Nature of Liquid: Polar liquids with strong forces boil at higher temperatures than non‑polar liquids.
3. Intermolecular Forces: Stronger forces → higher boiling point, as more energy is needed to equal external pressure.
Q16. What is density, how the density of liquid is affected by temperature and pressure?
OR
What is plasma? Explain plasma with the daily life examples?
OR
Explain importance of Silver and Gold.
📘 Answer (i) Density
• ⚖️ Density = Mass ÷ Volume.
• 🌡️ In liquids, density decreases with rise in temperature (expansion).
• ⬆️ Pressure slightly increases density by compressing molecules.
📘 Answer (ii) Plasma
• ⚡ Plasma is the fourth state of matter with free ions and electrons.
• 🔌 Daily life examples: fluorescent lamps, neon signs, lightning, stars, and the sun.
📘 Answer (iii) Importance of Silver & Gold
• 🪙 Silver: Used in jewellery, coins, mirrors, photography, and electronics.
• 👑 Gold: Valuable for jewellery, currency, investment, dentistry, and electronics.
• 🌟 Both are precious metals with cultural, economic, and industrial importance.
Q17. Describe the construction of electrochemical cell. Write down names of two types of electrochemical cells. Write down 4 applications of electrolytic cells or electrolysis.
⚙️ Construction
• An electrochemical cell consists of two electrodes (anode & cathode) dipped in electrolyte.
• Connected externally by a wire and internally by a salt bridge to complete the circuit.
• Chemical energy is converted into electrical energy.
📘 Types of Electrochemical Cells
• 🔋 Galvanic (Voltaic) Cell
• ⚡ Electrolytic Cell
🌟 Applications of Electrolytic Cells
• 🪙 Electroplating metals (e.g., silver, gold).
• ⚡ Extraction of metals (e.g., sodium, aluminium).
• 💡 Electrolysis of water to produce hydrogen & oxygen.
• 🧪 Purification of metals (e.g., copper).
Q18. Give reason:
(i) Why gasoline does not dissolve in water?
(ii) Alkali metals are not found in free state in nature, why?
(iii) Why ionic compounds conduct electricity in molten or in aqueous solutions only?
(iv) Why the solubility of a salt increases with the increase in temperature?
(v) Explain why table salt has a very high melting point.
(vi) Atomic radii increase down a group and decrease across a period.
(vii) Alkali metals have the largest while halogens have the smallest atomic radii in their period.
(viii) Shielding effect of inner electrons remains the same across a period.
(ix) Ionization energy, electron affinity and electronegativity show same trends across a period.
(x) Covalent bonds are strong and hard to break but why most of the covalent compounds have low melting and boiling points.
(xi) Why the rate of diffusion of gases is rapid than that of liquids?
(xii) How does electron differ from proton or neutron?
(xiii) Helium diffuses faster than methane.
📘 Answer
(i) 💧 Gasoline is non‑polar, water is polar → they don’t mix.
(ii) ⚡ Alkali metals are highly reactive → always found in compounds.
(iii) 🔋 Free ions exist only in molten/aqueous state → conduct electricity.
(iv) 🌡️ Higher temperature increases solubility by providing energy to break lattice.
(v) 🧂 Strong ionic bonds in NaCl → very high melting point.
(vi) 📏 Down group size ↑ (more shells), across period size ↓ (greater nuclear pull).
(vii) ⚙️ Alkali metals largest due to fewer protons; halogens smallest due to strong pull.
(viii) 🛡️ Shielding remains same across period → same inner shells.
(ix) 📈 IE, EA, EN all increase across period due to stronger nuclear attraction.
(x) 🔗 Covalent bonds strong, but weak intermolecular forces → low melting/boiling points.
(xi) 💨 Gases diffuse faster due to low density and weak intermolecular forces.
(xii) ⚡ Electron is negatively charged, very light; proton positive, neutron neutral and heavier.
(xiii) 🎈 Helium lighter than methane → diffuses faster.
Q6. What is the mass of oxalic acid (C₂H₂O₄) required to prepare 100 cm³ volume of 2M oxalic acid solution?
OR
What is the molarity of the solution prepared by dissolving 1.25 g of HCl gas into enough water to make 30 cm³ of solution?
📘 Solution (i) Mass of Oxalic Acid
Given: M = 2 M, V = 100 cm³ = 0.1 dm³, Molar mass = 90 g/mol
Formula: Mass = M × Molar mass × Volume
Calculation: 2 × 90 × 0.1 = 18 g
✅ Required mass = 18 g
📘 Solution (ii) Molarity of HCl
Given: Mass = 1.25 g, V = 30 cm³ = 0.03 dm³, Molar mass = 36.5 g/mol
Formula: M = Mass ÷ (Molar mass × Volume)
Calculation: 1.25 ÷ (36.5 × 0.03) = 1.14 mol/dm³
✅ Molarity = 1.14 M
Q11. The 800 cm³ of a gas is enclosed in a container under a pressure of 750 mm. If the volume is reduced to 250 cm³, what will be the pressure?
OR
📘 Solution
Given:
P₁ = 750 mm Hg
V₁ = 800 cm³
V₂ = 250 cm³
Required: P₂ = ?
Formula: P₁V₁ = P₂V₂ ⇒ P₂ = (P₁ × V₁) ÷ V₂
Calculation:
P₂ = (750 × 800) ÷ 250
P₂ = 2400 mm Hg
✅ Result: Decrease in volume increases the pressure.
OR
A sample of Hydrogen gas has a volume of 350 cm³ at 40 ºC. If gas is allowed to expand up to 700 cm³ at constant pressure. Find out its final temperature? (Answer: 626 K)
📘 Solution
Given:
V₁ = 350 cm³
V₂ = 700 cm³
T₁ = 40°C ⇒ 40 + 273 = 313 K
Required: T₂ = ?
Formula:
V₁ / T₁ = V₂ / T₂ ⇒ T₂ = (V₂ × T₁) ÷ V₁
Calculation:
T₂ = (700 × 313) ÷ 350 = 626 K
✅ Result: Final temperature of the gas is 626 K.
Q17. Determine the percentage concentration of the solution obtained by dissolving 10g sugar in 140g water.
OR
A solution of 20 cm³ of alcohol is dissolved in 80 cm³ of water. Calculate the concentration (v/v) of this solution.
📘 Solution (i) Mass Percent
Mass of solute (sugar): 10 g
Mass of solvent (water): 140 g
Total mass of solution: 10 + 140 = 150 g
Formula: Mass % = (Mass of solute / Mass of solution) × 100
Calculation: (10 / 150) × 100 = 6.66%
✅ Result: Concentration = 6.66% by mass
📘 Solution (ii) Volume Percent
Volume of solute (alcohol): 20 cm³
Total volume of solution: 20 + 80 = 100 cm³
Formula: Volume % = (Volume of solute / Volume of solution) × 100
Calculation: (20 / 150) × 100 = 13.33%
✅ Result: Concentration = 13.33% by volume
Q18. 10M HNO₃ solution is available in laboratory. How would you prepare 500 cm³ of 0.1M solution?
OR
A sample of sulphuric acid has the molarity 20M. How many cm³ of solution should you use to prepare 500 cm³ of 0.5M H₂SO₄? (Answer: 12.5 cm³)
📘 Solution (i) Dilution of HNO₃
Given: M₁ = 10 M, V₂ = 500 cm³, M₂ = 0.1 M, V₁ = ?
Formula: M₁V₁ = M₂V₂
Calculation: 10 × V₁ = 0.1 × 500 ⇒ V₁ = (0.1 × 500) ÷ 10 = 5 cm³
✅ Result: Take 5 cm³ of 10M HNO₃ and dilute to 500 cm³.
📘 Solution (ii) Dilution of H₂SO₄
Given: M₁ = 20 M, V₂ = 500 cm³, M₂ = 0.5 M, V₁ = ?
Formula: M₁V₁ = M₂V₂
Calculation: 20 × V₁ = 0.5 × 500 ⇒ V₁ = (0.5 × 500) ÷ 20 = 12.5 cm³
✅ Result: Take 12.5 cm³ of 20M H₂SO₄ and dilute to 500 cm³.
✏️ Smart Answers of Section-C (Long-Answer Questions)✏️
Q19. Discuss Rutherford’s Alpha particles scattering experiment & write down the postulates of his atomic model.
🧪 Rutherford’s Alpha-Particle Scattering Experiment
🔹 In 1911, Lord Rutherford performed the Gold Foil Experiment.
🔬 A beam of fast α-particles was directed at thin gold foil, with a ZnS screen to detect scattering.
👀 Observations
• Most α-particles passed straight through → atom mostly empty space.
• Some were slightly deflected → presence of positive center.
• Very few bounced back → dense nucleus exists.
🧠 Postulates of Rutherford’s Atomic Model
⚪ Atom is mostly empty space.
🔴 Nucleus is small, dense, and positively charged.
➕ Nucleus contains protons & neutrons (mass concentrated).
⚡ Electrons revolve around nucleus in circular orbits.
⚖️ Atom is electrically neutral (protons = electrons).
OR
Determine the demarcation of periodic table in to s, p, d and f blocks.
🧬 Demarcation of the Periodic Table into 4 Blocks based of electronic configuration
The modern periodic table is divided into four blocks based on the type of subshell into which the last (valence) electron enters ⚛️.
🔹 Main Classification
🟦 Representative Elements → s-block & p-block
🟪 Noble Gases → inactive p-block elements
🟩 Outer Transition Elements → d-block
🟨 Inner Transition Elements → f-block
1️⃣ Representative Elements (s-block & p-block)
📌 Definition: Elements of Group A (IA to VIIA) are called Representative / Main Group Elements.
Reason of Name: Their chemical properties depend mainly on valence electrons.
Location: They are located on the left and right sides of the periodic table.
🔹 General Valence Shell Configuration👉 ns¹⁻² to ns² np¹⁻⁵
🔹 Characteristics
⚙️ Include metals (IA, IIA, part of IIIA), non-metals, and metalloids (B, Si, Ge, As, Sb, Te).
🧲 Some are diamagnetic, others paramagnetic.
(a) 🟦 s-Block Elements
➡️Last electron enters s-orbital.
➡️Valence configuration: ns¹ to ns²
➡️Groups IA and IIA
➡️Located at the extreme left of the periodic table ⬅️
➡️Total 12 elements (excluding H)
(b) 🟪 p-Block Elements
➡️Last electron enters p-orbital.
➡️Valence configuration: ns² np¹–⁶
➡️Groups IIIA to VIIIA
➡️Located at the extreme right of the periodic table ➡️
➡️Total 30 elements (excluding He)
2️⃣ 🟣 Noble Gases (Inert Elements)
Position: Group 0 / VIIIA
Valence shell configuration: ns² np⁶ (except He → 1s²)
🌈 Colourless, monoatomic gases
❄️ Chemically inert / unreactive
🧲 Diamagnetic
⚖️ Exceptionally stable due to complete octet
3️⃣ 🟩 d-Block Elements (Outer Transition Elements)
📌 Definition: Elements in which the last electron enters (n–1)d orbital.
Valence configuration: (n–1)d¹⁻¹⁰ ns²
Position: Group B elements (placed between s and p-block)
🔹 Characteristics
🔩 All are metals
🔄 Show variable oxidation states
🎨 Form coloured compounds
🔗 Have strong tendency to form complex ions
🔹 Sub-division
➡️ Consist of 4 series, each having 10 elements:
➡️ 3d, 4d, 5d, and 6d series
4️⃣ 🟨 f-Block Elements (Inner Transition Elements)
📌 Definition: Elements in which the last electron enters inner (n–2)f orbital.
General configuration: (n–2)f¹⁻¹⁴ (n–1)d¹ ns²
🔹 Sub-division
The f-block consists of two series, placed separately at the bottom of the periodic table ⬇️:
(a) 🔶 Lanthanides (4f-series): Follow element ₅₇La
Period: 6th
Members: ₅₈Ce to ₇₁Lu
(b) 🔷 Actinides (5f-series): Follow element ₈₉Ac
Period: 7th
Members: ₉₀Th to ₁₀₃Lr
OR
State modern periodic law. Explain periods in the modern periodic table.
🧪 Modern Periodic Law
📌 Statement
Modern Periodic Law states that:
👉 “The physical and chemical properties of elements are a periodic function of their atomic numbers.” ⚛️
🔹 This means when elements are arranged in increasing order of atomic number, their properties repeat at regular intervals.
📊 Periods in the Modern Periodic Table
📌 Definition
Horizontal rows in the modern periodic table are called periods ➡️.
There are 7 periods in total.
🔢 Explanation of Periods
🔹 General Characteristics of Periods
• All elements in a period have the same number of electron shells.
• Atomic number increases by one from left to right.
• Valence electrons increase gradually from 1 to 8 (except first period).
• Physical and chemical properties change gradually across a period.
🟦 Details of Each Period
1️⃣ First Period (Shortest Period)
🌟 Contains 2 elements: Hydrogen (H) and Helium (He).
🔹 Electrons occupy only the K-shell (n = 1).
2️⃣ Second Period
🌟 Contains 8 elements: Lithium (Li) to Neon (Ne).
🔹 Electrons enter L-shell (n = 2).
3️⃣ Third Period
🌟 Contains 8 elements: Sodium (Na) to Argon (Ar).
🔹 Electrons fill the M-shell (n = 3).
4️⃣ Fourth Period
🌟 Contains 18 elements: Potassium (K) to Krypton (Kr).
🔹 Electrons enter N-shell (n = 4).
⚙️ Includes d-block (transition) elements.
5️⃣ Fifth Period
🌟 Contains 18 elements: Rubidium (Rb) to Xenon (Xe).
🔹 Electrons fill the O-shell (n = 5).
⚙️ Also contains transition elements.
6️⃣ Sixth Period
🌟 Contains 32 elements.
🔹 Electrons enter P-shell (n = 6).
🔷 Includes Lanthanide (4f-block) series.
7️⃣ Seventh Period (Incomplete Period)
🌟 Contains 32 elements (some radioactive ☢️).
🔹 Electrons enter Q-shell (n = 7).
🔶 Includes Actinide (5f-block) series.
⚠️ Many elements are unstable.
OR
Write down 7 postulates of Bohr’s atomic model.
⚛️ Bohr’s Atomic Model – Postulates
1️⃣ Electrons revolve around the nucleus
🌀 Electrons move around the nucleus in fixed circular paths called orbits or energy levels.
________________________________________
2️⃣ Only certain orbits are permitted
🚫 Electrons can revolve only in specific allowed orbits and not in between.
________________________________________
3️⃣ Energy of electrons is quantized
⚡ Each orbit has a definite fixed energy, also called a stationary state.
________________________________________
4️⃣ No radiation in a stationary orbit
🔒 Electrons neither lose nor gain energy while moving in a permitted orbit, keeping the atom stable.
________________________________________
5️⃣ Emission or absorption of energy
📈 Energy is absorbed when an electron jumps from a lower to a higher orbit.
📉 Energy is emitted when it falls from a higher to a lower orbit.
________________________________________
6️⃣ Energy change occurs in the form of quanta
🌈 The energy absorbed or emitted is given by:
👉 ΔE = E₂ − E₁ = hν (where h = Planck’s constant, ν = frequency of radiation).
________________________________________
7️⃣ Quantization of angular momentum
🔄 The angular momentum of an electron in an orbit is quantized and given by:
👉 mvr = nh/2π (where n = integer, h = Planck’s constant).
This condition explains why only certain orbits are stable.
20. Define ionic bond. Discuss the formation of sodium chloride (NaCl).
Answer
🔗 Ionic Bond (Electrovalent Bond)
📌 Definition
An ionic (electrovalent) bond is the electrostatic force of attraction between oppositely charged ions, formed due to the complete transfer of one or more valence electrons from one atom to another ⚡.
🧂 Formation of Ionic Bond in Sodium Chloride (NaCl)
🔹 Condition for Ionic Bond Formation: ΔE.N. > 1.7.
🔹 For Na and Cl, ΔE.N. = 2.1, hence ionic bond formation is favored ✅.
Overall reaction can be shown as:
Na• (2,8,1) + : °Ċ˙̈̊ͦ: (2,8,7) → Na⁺Cl⁻ (2,8 Na⁺ for and 2,8,8 for Cl⁻)
⚙️ Steps Involved in the Formation of NaCl
🟦 Step I: Formation of Sodium Ion (Na⁺)
➡️ Sodium (Na) belongs to Group IA of the periodic table.
➡️ Electronic configuration of Na:👉 2, 8, 1
➡️ Sodium has one valence electron, which it loses easily.
➡️ By losing one electron, Na attains noble gas (Ne) configuration and forms a sodium cation (Na⁺).
📘 Reaction: Na(g) [2,8,1 ] → e⁻ + Na⁺(g) (2,8 like [Ne])
🟩 Step II: Formation of Chloride Ion (Cl⁻)
➡️Chlorine (Cl) belongs to Group VIIA of the periodic table.
➡️Electronic configuration of Cl:👉 2, 8, 7
➡️ Chlorine has 7 valence electrons and requires one electron to complete octet.
➡️ It gains the electron lost by sodium, attaining argon (Ar) configuration, and forms a chloride ion (Cl⁻).
📘 Reaction: Cl(g) [2,8,7]+ e⁻ → Cl⁻(g) (2,8,8 like [Ar])
🟨 Step III: Formation of Ionic Bond & Crystal Lattice
➡️ The positively charged Na⁺ ion and negatively charged Cl⁻ ion attract each other.
➡️ This electrostatic force of attraction results in the formation of an ionic bond.
➡️ A stable crystal lattice of sodium chloride (NaCl) is formed 🧂.
📘 Final Reaction: Na⁺(g) + Cl⁻(g) → NaCl(s)
OR
What is meant by covalent bond and coordinate covalent bond? Describe the formation of a covalent bond between two nonmetallic atoms. Explain single, double and triple covalent bond with examples. Explain dative bond with two examples.
Answer
🔗 Covalent Bond and Coordinate (Dative) Covalent Bond
🧪 Covalent Bond
📌 Definition
A covalent bond is formed by the mutual sharing of electrons between two atoms.
In this bond, electrons are neither gained nor lost.
⚛️ Covalent bonding occurs mainly between same or different non‑metallic atoms.
⚙️ Formation of a Covalent Bond (Hydrogen Molecule – H₂)
➡️ Each hydrogen atom has one valence electron.
➡️ Two hydrogen atoms share one pair of electrons.
➡️ By sharing electrons, both atoms attain a stable helium‑like configuration (duplet).
➡️ The shared pair of electrons forms a single covalent bond, represented by a single line (–) 👉 H – H
1️⃣ Single Covalent Bond
📌 Definition: Formed by mutual sharing of one bond pair (two electrons) between two atoms.
🔹 Representation: Denoted by a single short line (–).
🔹 Examples: H–H, F–F, Cl–Cl, H–Cl (HX), H₂O 💧, H₂S, NH₃, PH₃, NCl₃, CH₄, CCl₄, CH₃Cl, CH₃–CH₃, BF₃, AlCl₃, FeCl₃ etc.
🧪 Formation of Chlorine Molecule (Cl₂)
2️⃣ Double Covalent Bond
📌 Definition: Formed by mutual sharing of two bond pairs (four electrons).
🔹 Representation: Denoted by two short lines (=).
🔹 Examples: O=O, CO₂ (O=C=O), C₂H₄ (H₂C=CH₂), CS₂ (S=C=S), SO₂, SO₃, NO₂.
🧪 Formation of Oxygen Molecule (O₂)
➡️ Each oxygen atom has six valence electrons.
➡️ Two oxygen atoms share two pairs of electrons.
➡️ Thus, a double covalent bond is formed, completing the octet of each oxygen atom.
3️⃣ Triple Covalent Bond
📌 Definition: Formed by mutual sharing of three bond pairs (six electrons).
🔹 Representation: Denoted by three short lines (≡).
🔹 Examples: N₂ (N≡N), C₂H₂ (HC≡CH), HCN (H–C≡N).
🧪 Formation of Nitrogen Molecule (N₂)
➡️ Each nitrogen atom has five valence electrons.
➡️ Two nitrogen atoms share three pairs of electrons.
➡️ A strong triple covalent bond is formed, making N₂ very stable 💪.
🔗 Coordinate (Dative) Covalent Bond (one‑sided sharing)
📌 Definition
A coordinate covalent (dative) bond is a special type of covalent bond in which:
The shared pair of electrons is donated by only one atom, while the other atom provides no electron.
🔹 Representation: Shown by an arrow (→) pointing from donor atom to acceptor atom.
🔹 Examples of Dative Bond
1️⃣ Ammonium Ion (NH₄⁺)
Nitrogen donates its lone pair of electrons to H⁺. 👉 N → H⁺
Oxygen donates its lone pair of electrons to H⁺. 👉 O → H⁺
Q21. Describe the Boyle's law or Charles’s law with example.
Answer
🧪 Boyle’s Law (Pressure–Volume Law)
Presenter: Robert Boyle(1662), explains the relationship between pressure and volume of a gas.
📌 Statements
➡️At constant temperature, the volume of a fixed mass of a gas is inversely proportional to its pressure.
👉 OR
➡️The product of pressure and volume of a given mass of a gas at constant temperature remains constant.
📐 Mathematical Expression
V ∝ 1 / P (Temperature constant)
V = K × 1 / P (Removing proportionality sign (∝) by introducing a constant)
P × V = K (Constant)
📘 Where:
K = Proportionality constant (depends upon amount of gas, temperature, and units of P and V)
🔄 Second Form of Boyle’s Law
If pressure changes from P₁ to P₂ and volume from V₁ to V₂:
P₁V₁ = K …(1)
P₂V₂ = K …(2) [👉 Comparing equation (1) and (2).]
P₁V₁ = P₂V₂ = K
(Where: P₁ = initial pressure, P₂ = final pressure, V₁ = initial volume, V₂ = final volume)
🧪 Experimental Verification
The relationship between volume and pressure at constant temperature is shown in the following figure. Where given mass of a gas at constant temperature shows increase in volume by decrease in pressure. While increase in pressure decreases volume. But in both cases, the product of pressure and volume is constant.
Change in pressure (P)= 1.0, Change in volume (V) = 4; PV = K (Constant) = 1.0 × 4 = 4
Change in pressure (P): 2.0, Change in volume (V): 2; PV = K (Constant) = 2.0 × 2 = 4
In all cases, PV remains constant.
At constant temperature:
📉 Increase in pressure → 📉 Decrease in volume
📉 Decrease in pressure → 📈 Increase in volume
Conclusion: 🔹 Boyle’s law → Pressure ↑, Volume ↓ (T constant)
🧪 Charles’ Law (Volume–Temperature Law)
Presenter: Jacques Charles (1787) explains the relationship between volume and absolute temperature at constant pressure.
📌 Statement
The volume of a fixed mass of a gas is directly proportional to its absolute (Kelvin) temperature.
👉 OR
At constant pressure, the ratio of volume of a gas to its absolute temperature remains constant.
📐 Mathematical Expression
V ∝ T (Pressure constant)
V = KT (Removing proportionality sign by introducing a constant)
V / T = K (Constant)
📘 Where K is the proportionality constant.
🔄 Second Form of Charles’ Law
If volume changes from V₁ to V₂ and temperature from T₁ to T₂:
V₁ / T₁ = K …(1)
V₂ / T₂ = K …(2) 👉 Comparing (1) and (2):
V₁ / T₁ = V₂ / T₂ = K
🌡️ Absolute Temperature Scale (Kelvin Scale)
Introduced by Lord Kelvin.
➡️ Starts from 0 K (absolute zero).
➡️ 0 K = –273°C
➡️ At absolute zero, an ideal gas would have zero volume.
📘 Conversion formulas:
K = °C + 273
°C = K – 273
🧪 Experimental Verification & Example
According to Charles’ law:
If absolute temperature is doubled, volume also doubles (at constant pressure).
Example:
➡️ At 300 K, volume = V (2.5L)
➡️ At 600 K, volume = 2V (5.0 L)
Conclusion: Temperature ↑, Volume ↑ (P constant)
OR
Define vapour pressure. How equilibrium state involved in vapour pressure of liquids in close system? Describe the factors which affect on vapour pressure
Answer
🌫️ Vapour Pressure
📌 Definition
Vapour pressure is the pressure exerted by the vapours of a liquid when they are in equilibrium with its pure liquid at a given temperature.
⚖️ Equilibrium State & Origin of Vapour Pressure
Vapour pressure is observed only in a closed system 🔒.
In an open system, liquid molecules escape continuously and mix with air, so equilibrium is not established.
In a closed container:
💨 Liquid molecules evaporate into vapour.
🌧️ Vapour molecules condense back into liquid.
➡️ After some time, the rate of evaporation equals the rate of condensation.
➡️ At this stage, a dynamic equilibrium is established.
➡️ The pressure exerted by vapour molecules at equilibrium is called vapour pressure.
📐 Units of Vapour Pressure
🧪 mm of Hg
🌍 Atmosphere (atm)
⚖️ Torr
📏 Newton per meter square (N/m² or Pascal)
🔍 Factors Affecting Vapour Pressure
(i) 🌊 Nature of Liquid
Polar liquids → strong intermolecular forces → evaporate less easily → lower vapour pressure than non‑polar liquids
📌 Example
💧 Water (polar) → lower vapour pressure
🍷 Alcohol (less polar / non‑polar) → higher vapour pressure
(ii) 📏 Size of Molecules
Smaller molecules escape more easily from the liquid surface.
Therefore, smaller molecules have higher vapour pressure than larger ones.
📌 Example
Hexane (C₆H₁₄) → smaller molecule → higher vapour pressure
Decane (C₁₀H₂₂) → larger molecule → lower vapour pressure
(iii) 🌡️ Temperature
Rule: Vapour pressure increases with increase in temperature.
Reason: Higher temperature increases kinetic energy of molecules, causing faster evaporation.
📌 Example
Vapour pressure of water:
At 0°C → 4.58 mm Hg
At 100°C → 760 mm Hg
Q22. Define the term solubility. How does nature of solute and solvent determine the extent of dissolution? Why the solubility of a salt increases with the increase in temperature?
Answer
🧪 Definition
Solubility is the amount of solute (g) that dissolves in 100 g or 100 mL of solvent to make a saturated solution at room temperature.
Units:
➡️ g/100 g water or g/100 mL water 🌊
➡️ mol/L or mol/dm³ (The practical and S.I. unit) ⚛️
⚡ Factors Affecting Solubility
➡️ Nature of solute & solvent 🧩
➡️ Temperature 🌡️
➡️ Pressure 💨
1️⃣ Effect of Nature of Solute & Solvent / General Principles of Solubility
Principle: “Like dissolves like” (Substances with similar intermolecular forces tend to dissolve in each other.) ✅
➡️ Polar or ionic solutes → dissolve in polar solvents 💧
➡️ Non‑polar solutes → dissolve in non‑polar solvents 🛢️
Examples:
➡️ Na₂CO₃, sugar, alcohol being polar → dissolve in water (polar) 🌊
➡️ Non‑polar substances → dissolve in non‑polar solvents, not in water ❌
2️⃣ Effect of Temperature
➡️ Solids in liquids: Solubility increases with temperature 🌡️🔥
Example: Hot water dissolves more sugar than cold water 🍬
➡️ Gases in liquids: Solubility decreases with temperature ❄️➡️🔥
Example: Air bubbles appear when warm water is poured into a glass 💨
OR
Discuss discharge tube experiment for the discovery of electrons with 4 properties of cathode rays.
Answer
✨ Discharge Tube Experiment & Discovery of Electrons ✨
🧪 Experiment: In a cathode ray discharge tube, when high voltage is applied between electrodes in a vacuum, a beam (cathode ray) travels from cathode (−) to anode (+). 💡 J.J. Thomson studied it and discovered electrons. ⚡
📋 4 Properties of Cathode Rays
➡️ Travel in straight lines in vacuum.
🖤 Negatively charged particles (electrons).
🌀 Cause magnetic & electric effects → can be deflected.
💥 Have mass → exert force on small objects.
✅ Conclusion: Cathode rays are streams of tiny negatively charged particles → electrons.
Q23. State and explain Faraday’s Laws of electrolysis.
Answer
✨ Faraday’s Laws of Electrolysis ✨
🧪 Faraday, a British chemist, discovered the relationship between electric current and the amount of substance deposited or liberated at electrodes. He formulated 2 important laws:
1️⃣ Faraday’s First Law of Electrolysis
📜 Statement:
The amount of substance deposited or released at an electrode is directly proportional to the quantity of electricity (Q) passed through the electrolyte. ⚡
🔢 Mathematical Form
w ∝ Q (Q= Quantity of electricity passed)
OR
w ∝ A × t [proportionality sign is removed by introducing a constant]
w = Z⋅A⋅t (or w = Z⋅Q)
Where:
w = mass of substance (kg or g)
Z = proportionality constant called electrochemical equivalent (E.C.E.) of substance 🟡
Q = total charge = current (A) × time (s) ⏱️
The electrochemical equivalent (Z) is the weight of the substance collected at the electrodes when one coulomb of electric charge is passed through the electrolyte (or 1 ampere electric current for 1 second).
Unit of Z: Its S.I. unit is kg/C and C.G.S. unit is g/C.
💡 Note: Each element has a unique Z, i.e., the mass deposited per coulomb of charge.
2️⃣ Faraday’s Second Law of Electrolysis
📜 Statement:
For the same quantity of electricity, the amounts of different substances deposited are proportional to their chemical equivalent masses. ⚖️
Mass deposited ∝ Chemical equivalent for different elements under same Q.
💎 Chemical Equivalent (e or C.E)
It is the mass of an element deposited by 1 Faraday (F = 96500 C) of electric charge. 1 Faraday of charge deposits 1 gram equivalent of a substance.
Equivalent weight of element = atomic weight / valency
📌 Examples:
Equivalent Mass / chemical equivalent of Al = 27(g)/3 = 9 g
Equivalent Mass / chemical equivalent of Ag = 108/1 = 108 g
Equivalent Mass / chemical equivalent of Cu = 63.5/2 = 31.75 g
OR
What is electroplating? How steel object can be electroplated with zinc and silver?
Answer
✨ Electroplating ✨
📜 Definition:
Electroplating is the deposition of a thin layer of metal on the surface of another metal using electrolysis. ⚡
1️⃣ Zinc Plating / Galvanizing 🛡️
📜 Definition of galvanizing:
Coating a steel or iron object with metallic zinc via electrolysis (electroplating) is called galvanizing.
⚙️ Method of Galvanizing
Device used: electrolytic cell.
Cathode (−): Steel object to be coated
Anode (+): Pure zinc rod
Electrolyte: Potassium zinc cyanide, K₂Zn(CN)₄ producing zinc (Zn²⁺) ions
Battery: Connects anode and cathode
🛠️ Working
➡️ Zn from anode oxidizes → Zn²⁺ ions
➡️ Zn²⁺ ions in solution reduce at cathode → Zn deposited
🧪 Electrolytic Reactions
➡️ Ionization of electrolyte: K₂Zn(CN)₄ → 2K⁺ + Zn²⁺ + 4CN⁻
➡️ Anode Reaction (Oxidation): Zn(Anode) → Zn²⁺ + 2ē
➡️ Cathode Reaction (Reduction): Zn²⁺ + 2ē → Zn(cathode)
➡️ Overall Redox Reaction: Zn(anode) → Zn(cathode) 🔄
💡 Purpose: Protects steel from corrosion and gives a shiny surface.
2️⃣ Silver Plating / Silvering 🥈
📜 Definition:
Coating a steel or cheap metal object with metallic silver via electrolysis (electroplating) is called silvering.
⚙️ Method
➡️ Device used: Electrolytic cell.
➡️ Cathode (−): Steel object to be coated
➡️ Anode (+): Pure silver rod
➡️ Electrolyte: Aqueous AgCl solution producing silver (Ag⁺) ions
➡️ Battery: Connects anode and cathode
🛠️ Working
➡️ Ag⁺ ions in solution gain electrons → deposit on cathode
➡️ Silver anode loses electrons → forms Ag⁺ ions
🧪 Electrolytic Reactions
➡️ Ionization of electrolyte: AgCl → Ag⁺ + Cl⁻
➡️ Anode Reaction (Oxidation): Ag(Anode) → Ag⁺ + ē
➡️ Cathode Reaction (Reduction): Ag⁺ + ē → Ag(cathode)
➡️ Overall Redox Reaction: Ag(anode) → Ag(cathode) 🔄
💡 Purpose: Gives decorative, corrosion‑resistant silver coating.
Q25. Explain electronegative character of non-metals or electropositive character of metals. Discuss the reactivity of Halogens
Answer
✨ Electronegative & Electropositive Characters ✨
1️⃣ Electronegative Character of Non-Metals ⚡
📜 Definition:
It is tendency of a non-metal to gain electrons and form anions (X + ē → X⁻).
🔹 Reason of High electronegative character of Halogens
Reason: Small atomic size & high nuclear charge → attract electrons easily ⚡
Example: Cl + ē → Cl⁻
🔹 Factors Affecting Electronegativity:
📏 Atomic Size (Inversely proportional); Atomic size ⬇️ → Electronegativity ⬆️
⚡ Nuclear charge (Directly proportional); Nuclear charge ⬆️ → Electronegativity ⬆️
🔹 Periodic Trend / Periodic Variation:
➡️ Across a period → Electronegativity ⬆️ (smaller atoms, higher nuclear charge)
➡️ Down a group → Electronegativity ⬇️ (larger atoms, lesser nuclear charge)
🧪 Trend of Reactivity of Halogens
🔹 Trend: Reactivity ⬇️ down the group (F₂ > Cl₂ > Br₂ > I₂)
Reason: Increasing atomic size and decreasing electronegativity down the group.
🔹 Key Reactions:
1️⃣ Oxidizing Power / Oxidizing Agents:
Reason: Halogens accept electrons easily acting as oxidizing agents.
⚡ 2Na + Cl₂ → 2NaCl
⚡ 2K + I₂ → 2KI
Order of Oxidizing Power down the group: Decreases; F₂ (most reactive) > Cl₂ > Br₂ > I₂ (least reactive)
Example: Fluorine being most reactive can displace other Halogens due to its highest oxidizing power.
🔄 Displacement Reactions:
More reactive halogen displaces less reactive.
• 2KI + Cl₂ → 2KCl + I₂
• 2KCl + F₂ → 2KF + Cl₂
• 2KBr + F₂ → 2KF + Br₂
➕ Addition with Hydrogen: Form halogen acids
H₂ + X₂ → 2HX (X = F, Cl, Br, I)
🔹 Acidic Strength of HX:
Order of acid strength: HI > HBr > HCl > HF
Reason: Increasing size of the halogen atom down the group.
HF weakest → Strong H‑bonding, doesn’t ionize easily and donate proton in water.
2️⃣ Electropositivity of Metals 🔋
📜 Definition:
Tendency of a metal to lose electrons and form cations (M → Mⁿ⁺ + nē).
Reason:
Metals are highly electropositive, due to this property they easily lose their valence shell electrons.
Example: Al → Al³⁺ + 3ē ⚡
🔹 Relation to Metallic Character:
Greater electropositivity → stronger metallic nature.
🔹 Factors Affecting Electropositivity:
📏 Larger size and weaker effective nuclear charge increase metallic character.
➡️ Ionization potential (Inversely proportional); Ionization energy ⬇️ → Electropositivity ⬆️
➡️ Atomic Size (Directly proportional); Atomic size ⬆️ → Electropositivity ⬆️
🔹 Periodic Trend / Periodic Variation:
Increases down a group with increasing atomic size due to fall in I.P. values.
Example:
• Electropositivity K > Na (Group IA) due to low I.P of K.
• Electropositivity Al > B (Group IIIA) due to low I.P of Al.
🔹 High Reactivity of Alkali Metals:
➡️ ns¹ configuration → low ionization energy → lose electron easily → Highly electropositive and strong reducing agents.
➡️ Highly reactive → Never found free in nature 🌍.
OR
What are transition elements? Give their types. Give their 4 general properties.
Answer
✨ Transition Elements ✨
📜 Definition:
Elements in which, besides the valence shell, the penultimate shell is also incomplete (electrons occupy d or f orbitals) are called transition elements. ⚡
📘 Classification / Types of Transition Elements
🔹 Outer Transition Elements (d-block)
➡️ Sub-group B elements (IB, IIB → IIIB to VIIIB)
➡️ Partially filled penultimate d-subshell + outer s-subshell
➡️ 4 series of 10 elements each
🔹 Inner Transition Elements (f-block)
➡️ Elements with partially filled f-subshell + outer s-subshell
➡️ Placed at the bottom of periodic table ⬇️
➡️ 2 series of 14 elements each
⚙️ General Properties of Transition Elements
🛠️ All are metals
🔋 Show variable valencies (e.g., Cu⁺ / Cu²⁺, Fe²⁺ / Fe³⁺)
🌈 Form coloured compounds (e.g., Fe³⁺ salts are brown)
🧲 Paramagnetic (except Zn, Cd, Hg → diamagnetic)
Q26. Explain the experiment to test CO₃²⁻, Cl⁻ and I⁻ ions and Zn²⁺, Mg²⁺, Ca²⁺ and Ba²⁺ ions.
Answer
🧪 Tests for Anions
| ⚙️ Experiment | 👀 Observation | ✅ Result |
|---|---|---|
| Test for CO₃²⁻ Sample solid + dilute mineral acid |
💨 Bubbles come out which turn lime water milky | CO₃²⁻ is present |
| Test for Cl⁻ Salt solution + dilute HNO₃ + AgNO₃ solution |
⚪ White ppt (AgCl) forms Soluble in NH₄OH |
Cl⁻ ion is present |
| Test for I⁻ Salt solution + dilute HNO₃ + AgNO₃ solution |
💛 Yellow ppt (AgI) forms Insoluble in excess NH₄OH |
I⁻ ion is present |
🧪 Tests for Cations
| ⚙️ Experiment | 👀 Observation | ✅ Result |
|---|---|---|
| Test for Zn²⁺ Salt solution + NH₄OH solution |
⚪ White ppt (Zn(OH)₂) White ppt dissolves in excess NH₄OH/NaOH → clear solution |
Zn²⁺ may be present |
| Test for NH₄⁺ Salt solution + NaOH solution + warm |
🌬️ Pungent smell of NH₃ released | NH₄⁺ ion may be present |
| Test for Ca²⁺ and Ba²⁺ Flame test using nichrome wire |
🍏 Apple green flame → Ba²⁺ 🧱 Brick red flame → Ca²⁺ |
Ba²⁺ and Ca²⁺ are present |
OR
What is allotropy? Describe different allotropes of carbon.
Answer
🧪 Allotropy
📌 Definition
Allotropy is the phenomenon in which an element exists in two or more different physical forms in the same physical state, having different properties but same chemical nature ⚛️.
🟤 Allotropes of Carbon
Carbon shows allotropy and exists in different forms, mainly classified as crystalline and amorphous.
🔹Crystalline Allotropes of Carbon
1️⃣ Diamond 💎
• Hardest natural substance
• Each carbon atom is covalently bonded to four other carbon atoms
• Poor conductor of electricity
• Used in cutting tools and jewellery
2️⃣ Graphite ✏️
• Soft and slippery
• Each carbon atom is bonded to three other carbon atoms
• Good conductor of electricity
• Used in pencils, lubricants, and electrodes
3️⃣ Fullerenes (C₆₀) ⚽
• Spherical structure
• Carbon atoms arranged in pentagons and hexagons
• Used in nanotechnology and medicines
OR
Describe the construction and working of lead battery or dry cell.
Answer
🔋 Lead Storage Battery
📌 Construction
A lead storage battery consists of:
• Positive plate: Lead dioxide (PbO₂) 🟤
• Negative plate: Spongy lead (Pb) ⚫
• Plates are immersed in an electrolyte of dilute sulphuric acid (H₂SO₄).
• Plates are separated by porous insulating separators.
• The whole arrangement is kept in a hard rubber or plastic container.
⚙️ Working of Lead Battery
🔹 During Discharging
• When the battery supplies current: Both plates convert into lead sulphate (PbSO₄).
• Sulphuric acid concentration decreases.
⚡ Reactions:
At negative plate: Pb + SO₄²⁻ → PbSO₄ + 2e⁻
At positive plate: PbO₂ + 4H⁺ + SO₄²⁻ + 2e⁻ → PbSO₄ + 2H₂O
🔹 During Charging
• When external DC source is applied: PbSO₄ changes back into PbO₂ (positive plate) and Pb (negative plate).
• Strength of sulphuric acid increases.
👉 This makes the process reversible ♻️.
📌 Uses
🚗 Automobiles
🔋 UPS and inverters
🔋 Dry Cell (Leclanché Cell)
📌 Construction
• A zinc container acts as the negative electrode (anode).
• A carbon rod acts as the positive electrode (cathode).
• The electrolyte is a moist paste of ammonium chloride (NH₄Cl).
• A mixture of manganese dioxide (MnO₂) and carbon powder surrounds the carbon rod.
• The cell is sealed from the top to prevent leakage.
⚙️ Working of Dry Cell
• When the circuit is completed: Zinc container loses electrons and forms Zn²⁺ ions.
• Electrons flow through the external circuit to the carbon rod.
⚡ Reactions:
At anode (Zn): Zn → Zn²⁺ + 2e⁻
At cathode (C): 2MnO₂ + 2NH₄⁺ + 2e⁻ → Mn₂O₃ + 2NH₃ + H₂O
MnO₂ acts as a depolarizer, preventing hydrogen accumulation.
📌 Characteristics / Uses
🔦 Small, light, and portable
📻 Used in torches, clocks, radios, toys
Q27. What are molecules? Discuss its six types with examples.
Answer
🔹 Molecules
📌 Definition
A molecule is the smallest particle of a substance that can exist independently and retains the chemical properties of that substance ⚛️.
Molecules are formed by atoms of the same or different elements chemically bonded together.
🧩 Types / Classification of Molecules based on composition
🟢 1. Homoatomic Molecules
➡️ Made of same type of atoms only
🧬 Examples: H₂, O₂, N₂, F₂, Cl₂, Br₂, I₂, O₃, P₄, S₄, S₆, S₈
🟢 2. Heteroatomic Molecules
➡️ Made of different types of atoms
🧬 Examples: CO, NO, H₂O, CO₂, NH₃, CH₄ etc.
🟢 3. Monoatomic Molecules
➡️ Consist of one atom (generally noble gases)
🧬 Examples: He, Ne, Ar, Kr, Xe, Rn
🟢 4. Diatomic Molecules
➡️ Consist of two atoms (of the same or different element)
🧬 Examples: H₂, O₂, N₂, F₂, Cl₂, Br₂, I₂, CO, NO, HF, HCl etc.
🟢 5. Triatomic Molecules
➡️ Consist of three atoms
🧬 Examples: O₃ (Ozone), H₂O, CO₂
🟢 6. Polyatomic Molecules
➡️ Consist of more than four atoms.
🧬 Examples: P₄, S₄, S₆, S₈, NH₃ (ammonia), CH₄ (methane), C₂H₆ (ethane), H₂SO₄, C₆H₁₂O₆ etc.
OR
What are mixtures? Give its examples. Discuss its two types with examples.
Answer
🔹 Mixtures
📌 Definition
A mixture is an impure substance which is a combination of two or more substances united physically without any fixed ratio in which each substance retains its own chemical properties ⚛️.
➡️ Components can be physically separated.
➡️ They do not have uniform composition.
➡️ The melting and boiling points of mixture are not sharp.
📌 Examples of Mixtures
➡️ Air (O₂ + N₂ + CO₂ + other gases) 🌬️
➡️ Salt + Sugar 🧂+🍬
➡️ Sand + Iron filings 🏖️+🧲
🧩 Types of Mixtures
Mixtures are mainly classified into two types:
1️⃣ Homogeneous Mixtures (Solution)
📌 Definition: Composition is uniform throughout, and individual components are not visible.
Also known as solutions or alloys.
🧬 Examples: Salt in water 🧂💧, Sugar in water (aqueous sugar solution) 🍬💧, Air 🌬️ etc.
2️⃣ Heterogeneous Mixtures
📌 Definition: Composition is not uniform, and individual components can be seen.
🧬 Examples: Soil 🌍, rocks 🪨, ice cream 🍨, chocolate chip cookies 🍪, pizza 🍕, rocks etc.
Q28. Compare reactivity of Alkali and Alkaline Earth Metals
Answer
⚡ Comparison of Reactivity
| 🔋 Alkali Metals (IA group) | 🧪 Alkaline Earth Metals (IIA group) |
|---|---|
| 1️⃣ Highly reactive & electropositive due to low ionization energy. | Less reactive & less electropositive due to high ionization energy. |
| 2️⃣ Form monovalent cation (M⁺). | Form divalent cation (M²⁺). |
| 3️⃣ React violently with halogens giving halides. ⚡ 2Na + Cl₂ → 2NaCl |
React slowly with halogens forming halides. ⚡ Ca + Cl₂ → CaCl₂ |
| 4️⃣ Immediately tarnish in air forming metal oxide. ⚡ 2K + O₂ → K₂O₂ |
React with oxygen on heating to form oxides. ⚡ 2Mg + O₂ → 2MgO |
| 5️⃣ React with water vigorously at room temperature forming strong alkaline solution + H₂. ⚡ 2K + 2H₂O → 2KOH + H₂ |
React with cold water less vigorously (more rapidly with hot water) forming weak alkaline solution. ⚡ Mg + H₂O → MgO + H₂ ⚡ MgO + H₂O → Mg(OH)₂ |
| 6️⃣ Oxides & hydroxides are more basic than those of IIA group. | Oxides & hydroxides are less basic than those of IA group. |
| 7️⃣ Do not form metal carbides. | Form metal carbides on heating. ⚡ Ca + 2C → CaC₂ |
Q29. Identify the highly electronegative and electropositive groups of the Periodic table. Enlist the elements present in these groups. Give four common characteristics of each of these groups.
Answer
⚡ Highly Electronegative & Electropositive Groups in the Periodic Table
⚛️ Highly Electronegative Group – Halogens (Group VIIA / 17) 🧪
📌 Elements: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (At)
✨ Characteristics
⚡ Strong tendency to gain electrons to form anions (X⁻).
⚡ Exist in all three physical states at room temperature: F₂, Cl₂ (gases), Br₂ (liquid), I₂ (solid).
⚡ Form salts with metals (e.g., NaCl, KBr).
⚡ Highly reactive, reactivity decreases down the group.
⚛️ Highly Electropositive Group – Alkali Metals (Group IA / 1) ⚡
📌 Elements: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), Francium (Fr)
✨ Characteristics
⚡ Strong tendency to lose electrons to form cations (M⁺).
⚡ Soft metals; can be cut with a knife 🔪.
⚡ Highly reactive with water, forming alkaline hydroxides (e.g., NaOH) and hydrogen gas 💧⚡.
⚡ Reactivity increases down the group; low melting and boiling points 🔥.
✏️ Extra Solved Questions✏️
Q24. Number of Moles & Molecules in 8 g of C₆H₁₂O₆ 🍬
Answer
📘 Solution
Given:
➡️ Mass of C₆H₁₂O₆ (molecular compound) = 8 g
➡️ Molar Mass of C₆H₁₂O₆ = (6×12) + (12×1) + (6×16) = 72 + 12 + 96 = 180 g/mol
REQUIRED:
➡️ Number of moles (n) of C₆H₁₂O₆ = ?
➡️ Number of molecules (Np) of C₆H₁₂O₆ = ?
🔹 Number of moles (n):
n = mass / molar mass = 8 / 180 = 0.044 mole ✅
🔹 Number of molecules (Np):
Np = n × Nᴀ = 0.044 × 6.02 × 10²³
= 2.68 × 10²² molecules ✅
Q. Calculate the number of moles, number of molecules and number of atoms present in 10 g of H₂SO₄
Answer
📘 Solution
➡️ Given mass of H₂SO₄ (molecular compound) = 10 g
➡️ Gram molecular (molar) mass of H₂SO₄ = (2×1) + (1×32) + (6×16) = 98 g/mol
➡️ Atomicity of H₂SO₄ (total atoms) = 2 + 1 + 4 = 7
REQUIRED:
• Number of moles (n) of H₂SO₄ = ?
• Number of molecules (Np) of H₂SO₄ = ?
• Number of atoms (Na) of H₂SO₄ = ?
🔹 Number of Moles (n)
n = mass / molar mass = 10 / 98 = 0.102 mole ✅
🔹 Number of Molecules (Np)
Np = n × Nᴀ = 0.102 × 6.02 × 10²³
= 6.14 × 10²² molecules ✅
🔹 Number of Atoms
Total atoms = Atomicity × Np = 7 × 6.14 × 10²²
= 4.298 × 10²³ atoms ✅
Q. Write chemical formulae of following compounds:
Answer
| 🧪 Compound | ⚡ Formula |
|---|---|
| Caustic soda | NaOH |
| Marsh gas | CH₄ |
| Caustic potash | KOH |
| Bleaching powder | CaOCl₂ |
| Baking soda | NaHCO₃ |
| Sulphur monochloride | S₂Cl₂ |
| Soda ash | Na₂CO₃ |
| Oleum | H₂S₂O₇ |
| Washing soda / Sodium carbonate | Na₂CO₃·10H₂O |
| Oil of vitriol | H₂SO₄ |
| Blue vitriol / Copper sulphate | CuSO₄·5H₂O |
| Aqua fortis | HNO₃ |
| Epsom salt / Magnesium sulphate | MgSO₄·7H₂O |
| Potash alum | K₂SO₄·Al₂(SO₄)₃·24H₂O |
| Gypsum | CaSO₄·2H₂O |
| Water glass | Na₂SiO₃ |
| Dolomite | MgCO₃·CaCO₃ |
| Pearl ash | K₂CO₃ |
| Carnalite | KCl·MgCl₂·6H₂O |
| Oxygenated water | H₂O₂ |
| Acetylene | C₂H₂ |
| Ethylene | C₂H₄ |
Q. Complete and balance the following equations:
Answer
⚡ Balanced Chemical Equations
2KClO₃ → 2KCl + 3O₂
3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O
2KNO₃ → 2KNO₂ + O₂
MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
2Ba(NO₃)₂ → 2BaO + 4NO₂ + O₂
Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O
2FeSO₄ → Fe₂O₃ + SO₂ + SO₃
4Zn + 10HNO₃ → 3H₂O + NH₄NO₃ + 4Zn(NO₃)₂
2Na + 2H₂O → 2NaOH + H₂
4NH₃ + 5O₂ → 4NO + 6H₂O
2NH₃ + 3Cl₂ → N₂ + 6HCl
4NH₃ + 7O₂ → 4NO₂ + 6H₂O
2Ca + O₂ → 2CaO
PCl₃ + 3H₂O → 3HCl + H₃PO₃
Write 4 differences between each of the following:
Difference between Alkali Metals and Halogens
Answer
| 📌 Property | 🔋 Alkali Metals (Group IA) | 🧪 Halogens (Group VIIA) |
|---|---|---|
| Nature of Elements | Solids and strongly electropositive (metallic) | Highly electronegative non‑metallic elements |
| No. of Valence Electrons | Contain 1 valence electron, monovalent | Contain 7 valence electrons, univalent |
| Valence Shell Configuration | ns¹ (where n = orbit ranges 2‑7) | ns² np⁵ |
| Reducing / Oxidizing Nature | Powerful reducing agents ⚡ | Powerful oxidizing agents ⚡ |
| Nature of Bond Formed | Form only ionic bonds 🔗 | Form ionic and covalent bonds 🔗 |
| Atomicity | Exist in monoatomic form e.g. Li, Na, K | Exist as diatomic molecules e.g. F₂, Cl₂, Br₂ |
| Nature of Oxides | Oxides (Na₂O) are basic in nature | Oxides are acidic in nature |
Difference between Solutions and Suspensions
Answer
| 📌 Property | 💧 Solutions | 🌫️ Suspensions |
|---|---|---|
| Size of constituent particles | 0.1–1 nm | Larger than 1000 nm |
| Visibility of particles | Cannot be seen with low power microscope 🔬 | Can be seen by low power microscope 🔬 |
| Separation of particles | Cannot be separated by filtration 🚫 | Can be separated by filtration ✅ |
| Settling of particles | Do not settle down | Settle down after some time ⏳ |
| Type of mixture | It is homogeneous ⚡ | It is heterogeneous ⚡ |
| Transparency | It is transparent ✨ | It is not transparent 🌫️ |
| Scattering of light (Tyndall effect) | Does not exhibit Tyndall effect 🚫 | Exhibits Tyndall effect i.e. particles scatter light 🌟 |
Difference between Ionic and Covalent Bond
Answer
| 📌 Property | 🔋 Ionic Bond | 🧪 Covalent Bond |
|---|---|---|
| Electron transfer or sharing | Formed by complete transference of electrons ⚡ | Formed by mutual sharing of one or more pairs of electrons 🤝 |
| Nature of bond | Electrostatic force of attraction between oppositely charged ions ⚡ | Force of attraction between electrons and nuclei of bonded atoms 🔗 |
| Constituent particles | Contains ions (cation & anion) ➕➖ | Does not contain ions |
| Chemical species | Formed between different atoms (metal + non‑metal) | Formed between same or different atoms (non‑metals) |
| Polarity | Always polar ⚡ | May be polar or non‑polar ⚖️ |
| Directional nature | Non‑directional bond ➡️ | Directional bond ↔️ |
| Difference in Electronegativity (EN) | EN difference > 1.7 | EN difference < 1.7 |
| Bond multiplicity | No bond multiplicity observed 🚫 | May be single, double or triple bond ➕➖➗ |
Distinction between Ionic and Covalent Compounds
Answer
| 📌 Property | 🔋 Ionic Compounds | 🧪 Covalent Compounds |
|---|---|---|
| State at room temperature | Solids, hard & rigid with strong interionic forces 🧱 | Exist as gas, liquid or solid with weak intermolecular forces 🌫️ |
| Dissociation in water | Dissociate into ions in water 💧 | Do not dissociate into ions in water 🚫 |
| Solubility | Soluble in polar solvents ⚡ | Insoluble in water 🚫 |
| Conductivity | Electrolytes (conduct electricity in solution) ⚡ | Mostly non‑electrolytes |
| Melting & boiling points | High, non‑volatile 🔥 | Low, volatile 🌡️ |
| Nature of compounds | Usually inorganic compounds ⚙️ | Usually organic compounds 🌱 |
| Examples | NaCl, KCl, MgO, Na₂S, etc. | H₂, CO₂, CH₄, HCl, H₂O etc. |
Difference between Polar and Non‑polar Bond
Answer
| 📌 S. # / Property | ⚡ Polar Bond | 🌐 Non‑polar Bond |
|---|---|---|
| 1 | Formed between two dissimilar atoms | Formed between two similar atoms |
| 2 | Small difference in electronegativity (ΔEN ≈ 0.5 – 1.7) | Electronegativity almost same (ΔEN < 0.5) |
| 3 | Shared electron pairs not uniformly attracted | Shared electron pairs uniformly attracted |
| 4 | Molecules containing polar bonds may or may not be polar | Molecules containing non‑polar bonds are always non‑polar |
| 5 | Covalent bond with partial ionic character (not purely covalent) | Pure covalent bond with no ionic character |
| 6 | Examples: Hδ⁺––Clδ⁻, Hδ⁺––Oδ⁻Hδ⁻, Cδ⁺=Oδ⁻ | Examples: H––H, N≡N, O=O, Cl––Cl |
Difference between Covalent Bond and Co‑ordinate Covalent Bond
Answer
| 📌 Property | 🔗 Covalent Bond | ➡️ Co‑ordinate Covalent Bond |
|---|---|---|
| 1 | Formed by mutual sharing of electrons between two atoms 🤝 | Formed by one‑sided sharing of electrons between bonded atoms ➡️ |
| 2 | Attraction between shared electron pairs and two nuclei | Attraction between lone pair of electrons and nuclei |
| 3 | Formed between like or unlike atoms | Formed between two unlike atoms |
| 4 | Both atoms share equal number of electrons ⚖️ | One atom donates lone pair, other accepts it 🎯 |
| 5 | May be polar or non‑polar | Always polar ⚡ |
| 6 | Associated with only covalent character | Associated with both covalent & ionic characters |
| 7 | May be single, double or triple bond (–, =, ≡) | Always a single bond ➡️ |
| 8 | Denoted by short lines (–, =, ≡) | Denoted by an arrow (→) pointing to acceptor atom |
| 9 | Covalent compounds usually insoluble in water 🚫💧 | Co‑ordinate covalent compounds sparingly soluble in water 💧 |
Sand (SiO₂), Limestone (CaCO₃), Sodium nitrate (NaNO₃), table salt (NaCl), sal ammoniac (NH₄Cl), Caustic soda (NaOH), caustic potash (KOH), washing soda (Na₂CO₃.10H₂O), baking soda (NaHCO₃), soda ash (Na₂CO₃), Epsom salt (MgSO₄.7H₂O), gypsum (CaSO₄.2H₂O), oleum (H₂S₂O₇), marsh gas (CH₄), blue vitriol (CuSO₄.5H₂O), sugar (C₁₂H₂₂O₁₁), ethyl alcohol(C₂H₅OH), Acetylene, Ethylene.
OR
What is coordinate covalent bond? Explain
with two examples.
OR
Define metallic bond. How are metallic bonds formed?
Q7. Write down any three points of atomic
model proposed by Schrodinger or Bohr.
Or
Describe wave particle duality of electron
of De Broglie Hypothesis? Prove that modern theory of De Broglie is related with Einstein and
Plank's equations.
OR
Give three properties of canal rays.
Q8. Write down electronic
configuration of 5B, 9F, 7N, 11Na, 13Al,
15P, 20Ca, 19K+, 8O2−, 16S2−, 12Mg2+,
17Cl−.
OR
Justify that Rutherford atomic model has
defects? What are Limitations of Bohr's Atomic Model?
OR
What is shielding effect? Explain how shielding effect influence the periodic trends?
Q9. Balance the
any three of the following chemical equations:
2KClO₃ → 2KCl + 3O₂
2Ba(NO₃)₂ → 2BaO + 4NO₂ + O₂
2Na + 2H₂O → 2NaOH + H₂
2NH₃ + 3Cl₂ → N₂ + 6HCl
MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
4NH₃ + 5O₂ → 4NO + 6H₂O
4Zn + 10HNO₃ → 3H₂O+ NH₄NO₃ + 4Zn(NO₃)₂
3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O
2KNO₃ → 2KNO₂ + O₂
Ca + 2H₂O → Ca(OH)₂ + H₂
2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O
OR
How
is electronegative value determined the formation of chemical bond? Describe ionic character in covalent bond.
OR
What is meant by bond pair, lone pair and unpaired electrons? How many unpaired electrons are there in oxygen atom and nitrogen atom? How many lone pairs are there in nitrogen molecule and oxygen molecule?
Q10. What is KMT? Give its main postulates with respect to three states
of matter.
OR
What is diffusion and Graham’s law
of diffusion of gases? Which gas from among CO2, CH₄ and
NH₃ will diffuse the fastest
and why? Give the reason.
OR
Define ionization energy or electron affinity. Describe trend in group and period with examples of any one them.
Q11. Differentiate between amorphous and
Crystalline Solids?
OR
Explain the solute-solvent interaction to prepare sodium chloride solution.
Q12. Define electrochemical reaction and redox
reaction. Write down 2 differences between oxidation and reduction and oxidizing agent and reducing agent with
examples. Give an example of redox reaction and also Identify oxidizing and reducing agents of
the following chemical reaction:
Zn + Cl₂ → ZnCl₂
OR
Differentiate
between electrolytes and non-electrolytes with examples. Identify strong and
weak electrolytes from the
following:
HCl (S), KI (S), NaOH (S), H₂S (W), CH₃COOH (W), NH₄OH (W), NaCl (S), C₂H5OH (W)
Q13.
What is corrosion of metal and rusting?
Name the methods which are used to protect metal from corrosion. How cathodic protection prevent metal from
corrosion?
OR
Write down the composition of following alloys:
Brass (Cu-Zn,[4:1]), Bronze (Cu-Sn-Zn) [9:1], Bell metal (Cu-Sn), Monel (Ni-Cu-Fe), Amalgam (Hg-Ag-Cu- Zn), Pewter (Sn-Cu-Pb-Sb-Bi), White gold (Au-Pb-Ag-Cu (18 karat), Duralumin (Al-Cu-Mg-Ni)
Q14.What are
metalloids? Write names and symbols of any 5 metalloids.
OR
Write names and symbols of some
noble metals. Explain inertness of noble metals.
OR
Define Moh Scale. What are Soft &
Hard Metals? Differentiate
between sodium and iron as soft and hard metal.
OR
Differentiate between metal and metals. Identify the elements as metals, non-metals and metalloids from the following: C, Ca, Sb, S, Sr, Se, K, P, N, Ba, Ge, I, Al, B, As
Q15. What is the boiling point? How boiling point is affected by different factors? How boiling point of a substance is affected by atmospheric pressure?
Q16. What is
density, how the density of liquid is affected by temperature and pressure?
OR
What is
plasma? Explain plasma with the daily life examples?
OR
Explain importance of Silver and gold.
Q17. Describe the construction of electrochemical cell. Write down names of two types of electrochemical cells. Write down 4 applications of electrolytic cells or electrolysis.
Q18. Give reason:
(i)
Why gasoline does not dissolve in water?
(ii)
Alkali metals are not found in free state in nature, why?
(iii)
Why ionic compounds conduct electricity in molten or in aqueous solutions only?
(iv)
Why the solubility of a salt increases with the increase in temperature?
(v)
Explain why table salt has a very high melting point.
(vi)
Atomic radii increase down a group and decrease across a period.
(vii)
Alkali metals have the largest while halogens have the smallest atomic radii in
their period.
(viii)
Shielding effect of inner electrons remains the same across a period.
(ix)
Ionization energy, electron affinity and electronegativity show same trends
across a period.
(x)
Covalent bonds are strong and hard to break but why most of the covalent
compounds have low melting and boiling
points.
(xi)
Why the rate of diffusion of gases is rapid than that of liquids?
(xii)
How does electron differ from proton or neutron?
(xiii)
Helium diffuses faster than methane.
Q19. Discuss Rutherford’s Alpha particles scattering experiment &
write down the postulates of his atomic model.
OR
Determine the demarcation of periodic table
in to s, p, d and f blocks.
OR
Write down 6 postulates of Bohr’s atomic model.
Q20. Define ionic bond. Discuss the formation of sodium chloride (NaCl) or
magnesium oxide.
OR
What is meant by covalent bond and coordinate covalent bond? Describe the formation of a covalent bond between two nonmetallic atoms. Explain single, double and triple covalent bond with examples. Explain dative bond with two examples.
Q21. Describe the
Boyle's law or Charles’s law with example.
OR
Define vapour pressure. How equilibrium state involved in vapour pressure of liquids in close system? Describe the factors which affect on vapour pressure
Q22. Define
the term solubility. How does nature of solute and solvent determine the extent
of dissolution? Why the solubility of a salt increases with the increase in
temperature?
OR
Discuss discharge tube experiment for the
discovery of electrons with 4 properties of cathode rays.
OR
Explain the importance of glues and epoxy resins in our society.
Q23. State
and explain Faraday’s Laws of electrolysis.
OR
What is electroplating? How steel object can be electroplated with zinc, tin and silver?
Q25. Explain electronegative character of non-metals or electropositive
character of metals. Discuss the reactivity of
Halogens
OR
What are transition elements? Give their types. Give their 4 general properties.
Q26.Explain the experiment to test CO32‒, Cl‒ and I‒ ions and Zn2+,
Mg2+, Ca2+ and Ba2+ ions.
OR
What
is allotropy? Describe different allotropes of carbon.
OR
Describe the construction and working of lead battery or dry cell.
Q27. What are molecules? Discuss its six types
with examples.
OR
What are mixtures? Gives its examples. Discuss its two types with examples.
Q28. Compare of reactivity of Alkali and Alkaline Earth Metals
Q29.Identify the highly electronegative and
electropositive groups of the Periodic table. Enlist the elements present in
these groups. Give four common characteristics of each of these groups.
🌈🔥Numericals
Q30. Calculate
the number of moles, number of molecules present in 8g of C6H12O6?
(answer; 0.04, 2.40 x 1022 molecules)
OR
Calculate
the number of moles, number of molecules and number of atoms present in 10 g of
H2SO4
(answer; 0.10 mole, 6.02 x 101022,
4.214 x 1023 atoms)
Q31.What is the
mass of oxalic acid (C2H2O4) required to
prepare 100 cm3 volume of 2M oxalic acid solution?
Or
What is the molarity of the solution prepared by dissolving 1.25 g of HCl gas into enough water to make 30 cm3 of solution?
Q32. Determine the percentage concentration of the
solution obtained by dissolving 10g sugar in 140g water
OR
A solution of 20 cm3 of alcohol is dissolved in 80cm3 of water. Calculate the concentration (v/v) of solution.
Q33. 10M HNO3 solution is
available in laboratory. How would you prepare 500 cm3 of 0.1M
solution?
OR
A sample of sulphuric acid has the molarity 20M. How many cm3 of solution should you use to prepare 500 cm3 of 0.5M H2SO4? (Answer; 12.5cm3)
Q34. The 800 cm3 of a gas is enclosed in a container
under a pressure of 750 mm. If the volume is reduced to 250 cm3, what will be the
pressure?
OR
A sample of Hydrogen gas has a volume of 350 cm3 at 40oC. If gas is allowed to expand up to 700 cm3 at constant pressure. Find out its final temperature? (answer; 626 K)
Q35. Calculate the number of atoms present in 9.2 g of calcium.
🌈🔥Important MCQs
1. Mole fraction is denoted by:
🟥A. X✅
🟦B. Z
🟩C. N
🟨D. M
🟩C. Sixtet
🟨D. None of them
3. At room temperature, most of the ionic compounds are:
🟥A. Amorphous Solid
🟦B. Crystalline Solid✅
🟩C. Liquid
🟨D. Gas
4. 101325 Pascal = …………. Atm
🟥A. 1✅
🟦B. 2
🟩C. 3
🟨D. ½
5. Which of the following gas diffuses faster?
🟥A. Oxygen
🟦B. Chlorine
🟩C. Fluorine
🟨D. Nitrogen✅
6. Hexane is an example of this type of solvent:
🟥A. Polar
🟦B. Non polar✅
🟩C. Ionic
🟨D. Universal
7. 12 g of magnesium (Mg) is equal to:
🟥A. 1 mole
🟦B. 2 moles
🟩C. 3 moles
🟨D. Half mole✅
8. The size of particles in suspension is:
🟥A. Greater than 10³ nm
🟦B. Less than 10³ nm
🟩C. 10² nm
🟨D. 10⁻²nm
9. This one of the following is non-electrolyte:
🟥A. Aqueous HCl
🟦B. Aqueous NaCl
🟩C. Benzene✅
🟨D. Molten KCl
10. This one is an alloy:
🟥A. Brass
🟦B. Steel
🟩C. Bronze
🟨D. All of them✅
11. 3 g equivalent weight of Al is equal to:
🟥A. 1 g
🟦B. 9 g
🟩C. 27 g✅
🟨D. 54 g
12. This gas turns lime water milky
🟥A. CO₂✅
🟦B. O₂
🟩C. NO₂
🟨D. N₂
13. This halogen exists in gaseous state:
🟥A. Fluorine
🟦B. Chlorine
🟩C. Iodine
🟨D. Both a and b✅
14. This element is metalloid:
🟥A. Br
🟦B. Sb✅
🟩C. S
🟨D. Sr
15. No Definite shape and definite volume is the property of:
🟥A. Gas
🟦B. Plasma
🟩C. Liquid✅
🟨D. Solid
16. The pH value of acidic solution is:
🟥A. Less than 7.0✅
🟦B. 7.0
🟩C. Greater than 7.0
🟨D. 14.0
17. The horizontal rows of elements in the Modern periodic table are called:
🟥A. Group
🟦B. Period✅
🟩C. Series
🟨D. Rows
18. W=Z x A x T, this equation was proved by:
🟥A. Michael Faraday✅
🟦B. Alexandro Volta
🟩C. Galvani
🟨D. Madam Currie
19. One Faraday is equal to:
🟥A. 96560 Coulombs✅
🟦B. 95650 Coulombs
🟩C. 96650 Coulombs
🟨D. None of these
20. It is the longest period of the periodic table:
🟥A. 2
🟦B. 6✅
🟩C. 7
🟨D. 59
21. In jellies, solute and solvent are:
🟥A. Sugar and water
🟦B. Water and fat
🟩C. Water & fruit pulp✅
🟨D. Air and water
🟦B. NH₄Cl✅
🟩C. CH₄
🟨D. CO₂
23. This acid is also known as "Vitamin-C":
🟥A. Ascorbic acid✅
🟦B. Acetic acid
🟩C. Carbonic acid
🟨D. Oxalic acid
24. Taste of acids are:
🟥A. Bitter✅
🟦B. Sour
🟩C. Sweet
🟨D. Neutral
25. Sugar is an example of:
🟥A. Strong Electrolyte
🟦B. Weak Electrolyte
🟩C. Non-Electrolyte✅
🟨D. Electrolyte
26. The process in which molecules escape from the surface of a liquid is called:
🟥A. Boiling
🟦B. Evaporation✅
🟩C. Sublimation
🟨D. Melting
27. Bases turns red litmus paper into:
🟥A. Pink Colour
🟦B. Orange Colour
🟩C. blue✅
🟨D. white
28. The symbol of Sodium is:
🟥A. S
🟦B. So
🟩C. Na✅
🟨D. Ne
29. C-14 has the Neutron:
🟥A. 14
🟦B. 12
🟩C. 8✅
🟨D. 7
30. Al₂O₃ is ………. in nature.
🟥A. Basic
🟦B. Acidic
🟩C. Amphoteric✅
🟨D. Neutral
31. The empirical formula of Glucose is:
🟥A. CH₂O✅
🟦B. C₂HO
🟩C. CHO
🟨D. CHO₂
32. 44 a.m.u of carbon dioxide is equal to:
🟥A. Molar Mass
🟦B. Molecular Mass✅
🟩C. Atomic Mass
🟨D. Mass Number
33. In NaCl crystal lattice each Na⁺ ion is surrounded by:
🟦B. 6 Na⁺ ions
🟩C. 8 Cl⁻ ions
🟨D. 12 Cl⁻ ions
34. Which one is oxidizing agent?
🟥A. Al
🟦B. H₂S
🟩C. Cl₂✅
🟨D. NaH
35. Which one of the following is a non-polar molecule?
🟥A. NH₃
🟦B. HCl
🟩C. CH₄✅
🟨D. H₂O
36. The empirical formula of formaldehyde is:
🟥A. CH₂O✅
🟦B. C₂HO
🟩C. CHO
🟨D. CHO₂
37. Which pair of elements is chemically similar?
🟥A. K, Cr
🟦B. Cu, Ca
🟩C. F, Cl✅
🟨D. N, O
38. One atmospheric pressure is equal to:
🟥A. 10325 Pascal
🟦B. 106075 Pascal
🟩C. 10523 Pascal
🟨D. 101325 Pascal✅
39. Which of the following have sharp melting point in solids?
🟥A. Plastic
🟦B. Rubber
🟩C. Glass
🟨D. Diamond✅
40. The shielding effect across the period:
🟥A. Increases
🟦B. Decreases
🟩C. Moderate
🟨D. Remain same✅
41. If nucleon number of potassium is 39, number of neutrons will be:
🟥A. 39
🟦B. 19
🟩C. 20✅
🟨D. 29
42. Which one of the following is most penetrating?
🟥A. Electron
🟦B. Proton
🟩C. alpha particle
🟨D. Neutron✅
43. If proton number is 19, electron configuration will be:
🟥A. 2, 8, 9
🟦B. 2, 8, 8, 1✅
🟩C. 2, 8, 1
🟨D. 2, 8, 3
44. Which one of the following is most penetrating?
🟥A. Beta particle
🟦B. Gamma rays✅
🟩C. alpha particle
🟨D. None
45. Name the material of screen which used in Rutherford atomic model:
🟥A. Aluminum foil
🟦B. Aluminum sulphide
🟩C. sodium sulphide
🟨D. zinc sulphide✅
46. 4th and 5th period in periodic table are known as
🟥A. Short period
🟦B. Long period✅
🟩C. Very long period
🟨D. Normal period
47. Which one of the following decreases along the period?
🟥A. Ionization Energy
🟦B. Atomic Radius✅
🟩C. Electronegativity
🟨D. Electron Affinity
48. The ionization energy across the period:
🟥A. Increases✅
🟦B. Decreases
🟩C. Moderate
🟨D. Remain
49. In group electron affinity values decreases from top to bottom because:
🟥A. Atomic size normal
🟦B. Atomic size increases✅
🟩C. Atomic size decreases
🟨D. Atomic size same
50. Interaction between highly electron deficient hydrogen and highly electronegative atom is called
🟥A. ionic bond
🟦B. metallic bond
🟩C. hydrogen bond✅
🟨D. covalent bond
51. Number of electrons lost by atoms of group IIIA equals:
🟥A. 1
🟦B. 2
🟩C. 3✅
🟨D. 4
52. Which of the following gas diffuses fastest?
🟥A. Ethene
🟦B. Methane✅
🟩C. Ammonia
🟨D. Ethyne
🟥A. HBr
🟦B. HF✅
🟩C. HI
🟨D. HCl
54. The vapour pressure of a liquid increases with the increase f:
🟥A. Polarity of molecules
🟦B. Temperature✅
🟩C. Intermolecular forces
🟨D. Pressure
55. One atmospheric pressure is equal to:
🟥A. 1 torr
🟦B. 760 torr✅
🟩C. 10.7 psi
🟨D. 101.325 Pascal
56. Which of the following have sharp melting point in solids?
🟥A. Glass
🟦B. NaCl✅
🟩C. Rubber
🟨D. Plastic
57. The density of gases increases when its:
🟥A. Temperature increased
🟦B. Pressure increased✅
🟩C. Volume increased
🟨D. None of these
58. Solubility is usually expressed in grams of the solute dissolved in ________gram of a solvent
🟥A. 10 grams
🟦B. 100 grams✅
🟩C. 500 grams
🟨D. 1000 grams
59. 2 moles of sodium chloride (NaCl) is equal to:
🟥A. 123 grams
🟦B. 117 grams✅
🟩C. 135 grams
🟨D. 158 grams
60. Molarity of a solution which is prepared by dissolving 40 g sodium chloride in 500cm³ of solution is:
🟥A. 1.33 M
🟦B. 1.36 M✅
🟩C. 1.5 M
🟨D. 1.4 M
61. Which solution contains more water?
🟥A. 1.0M
🟦B. 0.25M✅
🟩C. 0.75M
🟨D. 0.5M
62. Which one is oxidizing agent?
🟥A. Al
🟦B. NaH
🟩C. F₂✅
🟨D. H₂S
63. Chlorine can be displaced by _________
🟥A. Br
🟦B. I
🟩C. F✅
🟨D. At
64. Al₂O₃ and ZnO are ………. in nature.
🟥A. basic
🟦B. Neutral
🟩C. Amphoteric✅
🟨D. Acidic
65. Which one forms weak electrolyte solution with water?
🟥A. HCl
🟦B. KOH
🟩C. CH₃COOH✅
🟨D. NaCl
66. 1g equivalent weight of Al is equal to ……..
🟥A. 9 g✅
🟦B. 27 g
🟩C. 54 g
🟨D. 1 g
67. Which substance can conduct electricity by the movement of ions?
🟥A. Copper
🟦B. Graphite
🟩C. Sodium chloride✅
🟨D. Mercury
68. Which one metal belongs to alkaline earth metals?
🟥A. B
🟦B. Bi
🟩C. Br
🟨D. Ba✅
69. One Faraday = Coulombs
🟥A. 96500 Coulombs✅
🟦B. 96600 Coulombs
🟩C. 96700 Coulombs
🟨D. 96800 Coulombs
70. Number of molecules present in 18 grams of water (H₂O) is:
🟥A. 6.02 x 10²³✅
🟦B. 6.02 x 10²⁴
🟩C. 6.02 x 10³⁰
🟨D. 6.02 x 10³⁴
71. Symbol of Potassium is:
🟥A. P
🟦B. K✅
🟩C. S
🟨D. O
72. The number of electrons in S²⁻ is:
🟥A. 20
🟦B. 19
🟩C. 18✅
🟨D. 16
73. the 5th period of periodic table contains total ……………. elements.
🟥A. 32✅
🟦B. 8
🟩C. 18
🟨D. 2
74. Which one of the following diffuses faster than oxygen with molar mass of 32 g/mol?
🟥A. Cl₂
🟦B. F₂
🟩C. SO₂
🟨D. NH₃✅
75. Which one of the following is a non-polar molecule?
🟥A. NH₃
🟦B. HCl
🟩C. CO₂✅
🟨D. H₂O
76. The mass of 1 atom of diamond is equal to
🟥A. 1.99 x 10⁻²³ g✅
🟦B. 12 g
🟩C. 1.99 x 10²³ g
🟨D. 1.66 x 10⁻²⁴ g
77. The process of converting a solid into liquid at its melting point is called:
🟥A. Fusion✅
🟦B. Vaporization
🟩C. Evaporation
🟨D. Diffusion
78. Elements of group VII-A are known as:
🟥A. Alkaline Earth Metals
🟦B. Alkali Metals
🟩C. Halogens✅
🟨D. Inert gases
79. This one of the following is an ionic compound:
🟥A. H₂O
🟦B. NH₃
🟩C. NaCl (or KCl)✅
🟨D. CO₂
80. The only liquid metal is:
🟥A. Bromine
🟦B. Sodium
🟩C. Mercury✅
🟨D. Zinc
81. It is the heaviest sub-atomic particle:
🟥A. Photon
🟦B. Neutron✅
🟩C. Proton
🟨D. Electron
82. If nucleon number of calcium is 40, number of neutrons will be:
🟥A. 39
🟦B. 19
🟩C. 20✅
🟨D. 29
83. The isotope C-12 is present in abundance of:
🟥A. 96.9%
🟦B. 97.6%
🟩C. 98.8%✅
🟨D. 99.7%
84. Which one is metalloid?
🟥A. Br
🟦B. Se✅
🟩C. S
🟨D. Sr
85. CO₂ gas can turn ................................. milky.
🟥A. lime water ✅
🟦B. Caustic soda
🟩C. Caustic potash
🟨D. Quick lime
86. Which compound is known as lunar caustic?
🟥A. KNO₃
🟦B. AgNO₃✅
🟩C. NaOH
🟨D. NaNO₃
87. Which pair of elements is chemically similar?
🟥A. K, Cr
🟦B. Cu, Ca
🟩C. Mg, Ca✅
🟨D. N, O
88. Which one of the following is a non-polar molecule?
🟥A. NH₃
🟦B. HCl
🟩C. N₂✅
🟨D. H₂O
🟥A. Concentrated solution
🟦B. Saturated solution
🟩C. Standard solution✅
🟨D. Dilute solution
90. Alum is a
🟥A. Normal salt
🟦B. Double salt✅
🟩C. Mixed salt
🟨D. Basic salt
91. The pH value of human blood is:
🟦B. 7.8
🟩C. 7.2
🟨D. 7.0
92. A dative bond is always formed between the two:
🟦B. Similar atoms
🟩C. Unlike atoms✅
🟨D. Like atoms
93. A suspension of droplets of one liquid into another in which it is not soluble is called
🟥A. Foam
🟦B. Emulsion✅
🟩C. Mud
🟨D. Smoke
94. The number of moles of solute dissolved in per kilogram of solvent is called:
🟥A. Molarity
🟦B. Molality✅
🟩C. Normality
🟨D. Solubility
95. Gases possess neither definite shape nor definite:
🟥A. Mass
🟦B. Volume✅
🟩C. Density
🟨D. State
96. The process of converting a liquid into vapours at its boiling point is called:
🟥A. Fusion
🟦B. Vaporization✅
🟩C. Evaporation
🟨D. Diffusion
97. The force which holds atoms together in a molecule or crystal is called:
🟥A. Polar bond
🟦B. Dative bond
🟩C. Chemical bond✅
🟨D. Ionic bond
98. Elements of group VI-A are known as:
🟥A. Alkaline Earth Metals
🟦B. Chalcogens✅
🟩C. Halogens
🟨D. Inert gases
99. This one of the following is an ionic compound:
🟥A. H₂O
🟦B. NH₃
🟩C. MgO✅
🟨D. CO₂
100. The number of periods/series in Mendeleev’s periodic table is:
🟥A. 13
🟦B. 12✅
🟩C. 14
🟨D. 10
101. The only liquid non-metal is:
🟥A. Bromine✅
🟦B. Zinc
🟩C. Mercury
🟨D. Sodium
102. It is the lightest sub-atomic particle:
🟥A. Photon
🟦B. Neutron
🟩C. Proton
🟨D. Electron✅
103. The average mass number of all naturally found isotopes of an element is called:
🟥A. Atomic mass unit
🟦B. Atomic mass ✅
🟩C. Mass number
🟨D. Formula mass
104. In water (H₂O) the ratio by mass between Hydrogen and Oxygen is:
🟥A. 3:8
🟦B. 1:8✅
🟩C. 1:16
🟨D. 3:4
105. The empirical formula of Glucose is:
🟥A. CH₂O✅
🟦B. C₂HO
🟩C. CHO
🟨D. CHO₂
106. The study of Hydrocarbons and their derivatives is called:
🟥A. Inorganic Chemistry
🟦B. Physical Chemistry
🟩C. Organic Chemistry✅
🟨D. Biochemistry
107. It is the best disinfectant:
🟥A. Fluorine
🟦B. Iodine
🟩C. Bromine
🟨D. Chlorine✅
108. The bond formed by mutual sharing of electrons between the atoms is called:
🟥A. Electrovalent bond
🟦B. Covalent bond✅
🟩C. Dative bond
🟨D. Ionic bond
109. Electro-Chemical Equivalent of an element is represented by:
🟥A. M
🟦B. Z✅
🟩C. X
🟨D. N
110. Basic unit of electric current is
🟥A. coulomb
🟦B. joule
🟩C. ampere✅
🟨D. volt
111. The electronegativity of carbon is
🟥A. 2.1
🟦B. 3.0
🟩C. 2.5✅
🟨D. 1.0
112. Einstein’s mass energy equivalence is given by E =
🟥A. mv
🟦B. mc²✅
🟩C. mv²
🟨D. mc
113. Charge on an electron in coulomb is:
🟥A. 1.602 x 10⁻¹⁹✅
🟦B. 1.602 x 10⁻¹⁷
🟩C. 1.67 x 10⁻¹⁸
🟨D. 1.6 x 10⁻¹⁶
114. Which pair of elements is chemically similar?
🟥A. K, Cr
🟦B. Cu, Ca
🟩C. Ca, Sr✅
🟨D. N, O
(Litre) and is referred to as Molar Volume.
Q10. What is KMT? Give its main postulates with respect to three states of matter.
Answer
Definition
Boltzmann, Maxwell, Kelvin put forward kinetic molecular theory.
Kinetic molecular theory is a hypothetical but practical model which explains the general structures, composition and properties of all the three states of matter.
According to K.M.T, all matter is composed of extremely tiny particles called molecules which are always in a state of continuous random motion possessing kinetic energy. The three states of matter depend upon the arrangements, motions and forces of attraction between these particles.
Postulate of kinetic molecular theory for Gaseous state
1. The molecular are widely separated from each other.
2. The molecules have negligible volume.
3. The gas molecules are in constant random motion
4. The gas molecules move in straight line until they collide with each other or wall of container
5. The collisions of gas molecular are elastic in nature as during collision molecules do not lose energy
6. pressure produced when molecules collide with the wall of container
7. There are attractive and repulsive forces been molecules.
Postulate of kinetic molecular theory for liquid state
According to kinetic molecular theory liquid state shows following characteristics.
1. The molecules of a liquid are randomly arranged like gases.
2. The molecules of liquids have less kinetic energy than gases.
3. The molecules of liquids are fairly free to move.
4. The Liquids has no definite shape but assumes the shape of container.
5. The Boiling point of liquids depends on the external atmospheric pressure.
6. The Liquids are denser and not compressible like gasses.
Postulate of kinetic molecular theory for Solid state
According to kinetic molecular theory, solid state shows following characteristics:
1. The molecules in solids are closely packed due to stronger forces of attraction.
2. The molecules are unable to move freely as they have little space between them.
3. The molecules can vibrate and rotate in their fixed position.
4. Solids have definite shape definite volume
Q1. Calculate the number of moles, number of molecules present in 8g of C₆H₁₂O₆?
Solution
Given mass of C₆H₁₂O₆ (molecular compound) = 8 g
Gram molecular (molar) mass of C₆H₁₂O₆ = 6(12) + 12(1) + 6(16) = 72 + 12 + 96 = 180 g/mol
Number of moles (n) of C₆H₁₂O₆= ?
number of molecules (Nₚ) of C₆H₁₂O₆= ?
No. of moles (n) = mass/molar mass
No. of moles (n) = 8/180
No. of moles (n) = 0.044 mole
No of molecules = n x Nᴀ
No of molecules = 0.044 x 6.02 x 10²³
No of molecules = 0.268 x 6.02 x 10²³
No of molecules = 2.68 x 10²² molecules
OR
Calculate the number of moles, number of molecules and number of atoms present in 10 g of H₂SO₄
Solution
Given mass of H₂SO₄ (molecular compound) = 10 g
Gram molecular (molar) mass of H₂SO₄= 2(1) + 1(32) + 6 (16) = 98 g/mol
Atomicity of H₂SO₄ (total atoms) = 2+1+4 = 7
Number of moles (n) of H₂SO₄ =?
Number of molecules (Nₚ) of H₂SO₄ = ?
Number of atoms (Nₚ) of H₂SO₄ = ?
No. of moles (n) = mass/molar mass
No. of moles (n) = 10/98
No. of moles (n) = 0.102 mole
No of molecules = n x Nᴀ
No of molecules = 0.102 x 6.02 x 10²³
No of molecules = 0.614 x 6.02 x 10²³
No of molecules = 6.14 x 10²² molecules
No of atoms = Atomicity x Nᴀ
No of atoms = 7 x 6.14 x 10²²
No of atoms = 42.98 x 10²²
No of atoms = 4.298 x 10²³ atoms
SO₄? (Answer; 12.5cm³)
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Thank you so much sir❤ AAP hamary lia itni efforts kartay haay 🙃 or sir is model paper ki presentation bhi bhut best ha 👍sab kuch bhut easily samajh aa raha haay. Ap agar hamary lia asa arranged nhi karty to hamy pata nhi kitna dhondna parhta par kehtay ha teacher apny students ka lia cheaz ko asan banaya ha or aj dekh bhi lia sach maay sir I really like it bhut achi tarha sa ap ny ya sab Kia ha ❤🙃I really appreciate you Allah apka as jazbaa ko hamesha kaaim rakhy ameen ❤ or Allah ap jasa teachers ka saya ham pa hamesha banaya rakhy ameeeen ❤❤
ReplyDeleteThank you so much for your lovely feedback! It honestly made my day. I’m really happy to know that the explanation felt clear and helpful to you.
DeleteThanks again for visiting Learn Chemistry by Dr. Inam Jazbi. After teaching chemistry for more than 34 years, it always feels great when someone appreciates the effort put into sharing knowledge.
I truly appreciate your support. Stay blessed and keep learning! 🙏✨
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ReplyDeleteSir Hussain nice paper
DeleteSIR,sab se pehle to JAZAKALLAH for this aur ye guess paper bohat acha ha
ReplyDeleteALLAH apko in efforts ka ajar ata farmae
AMEEN
Thank you so much for your lovely feedback! It honestly made my day. I’m really happy to know that the explanation felt clear and helpful to you.
DeleteThanks again for visiting Learn Chemistry by Dr. Inam Jazbi. After teaching chemistry for more than 34 years, it always feels great when someone appreciates the effort put into sharing knowledge.
I truly appreciate your support. Stay blessed and keep learning! 🙏✨
Sir Hussain nice paper 📜
ReplyDeleteThank you so much sir this model paper is very helpful for students and the presentation was also very brilliant
ReplyDeletenice paper sir
ReplyDelete