IX Chemistry Guess Paper 2026 New Pattern| 100% Board Exam Important Questions & MCQs with Complete Solutions of All Questions

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Total marks: 60 

Time: 3 Hours

General Instructions

Section – A; contains 12 MCQs and all of them are to be answered.

Section – B; consists of 12 short-answer questions of which 8 are to be answered (24 marks)

Section – C; consists of 6 Long-answer questions of which 4are to be answered (24marks)

🌈🔥Section-B (Short-answer questions) 8 Questions 3 marks each (24)

Q1. Define any three of the following:

Valency, Electronegativity, electron affinity, Tyndall effect, 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.

Q2.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

(vii) Atom and molecule and ion

(viii) Molecule and molecular ion and free radical

(ix) Alkali metals and alkaline earths

(x) Cation and anion

(xi) Ion and free radical

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.

OR

What is chemistry? Define its main branches briefly.

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:

OR

Differentiate between empirical and molecular formula. 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:

Q4. Identify group and period in the periodic table of the following elements

(i) ₃Li or ₈O or ₁₅P

(ii) ₉F or ₁₁Na and ₁7Cl

(iii) ₁₂Mg or ₁₃ Al 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.

Q5. Write down one contribution of any 6 scientists in the field of chemistry.

OR

Draw the electronic dot and cross structures for H₂, N₂, O₂, CH₄, NH₃ and C₂H₂. 

Q6. Write chemical formulae and one use 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(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. 

🌈🔥Section-C (Long-answer questions) 4 Questions 6 marks each (24)

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 CO₃^2‒, 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 40^oC. 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

2. Noble gases are stable because their valance shell have complete (except Helium)

🟥A. Duplet

🟦B. Octet✅
🟩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

22. This one of the following compounds contains all three chemical bonds that are, Ionic, Covalent, Co- Ordinate Covalent Bond

🟥A. NaCl
🟦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:

🟥A. 6 Cl⁻ ions✅
🟦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

53. Which one is not strong acid?
🟥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 

89. Solution of known concentration is called:
🟥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: 

🟥A. 7.35-7.45✅
🟦B. 7.8
🟩C. 7.2
🟨D. 7.0

92. A dative bond is always formed between the two: 

🟥A. Like and unlike atoms
🟦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

115. Solutions are:

🟥A. Colloids

🟦B. Transparent✅

🟩C. Opaque

🟨D. None of these

116. Number of molecules present in 36 grams of water (H₂O) is:

🟥A. 6.02 x 10²³

🟦B. 2 x 6.02 x 10²³✅

🟩C. 3 x 6.02 x 10²³

🟨D. 6.02 x 10³⁴

117. Symbol of silicon is:

🟥A. S

🟦B. Se

🟩C. Si ✅

🟨D. Sc

118. Caca-cola contains this acid:

🟥A. Acetic acid

🟦B. Carbonic acid✅

🟩C. Formic acid

🟨D. Boric acid

119. The number of electrons in P³⁻ is:

🟥A. 20

🟦B. 19 

🟩C. 18 ✅

🟨D. 16 

120. Which one of the following gas is also known as marsh gas?

🟥A. Ethane

🟦B. Ethyne 

🟩C. Methane✅

🟨D. Ethene

121. Basic unit of electric charge is

🟥A.joule

🟦B.coulomb✅

🟩C.ampere

🟨D.Volt

122. The 5th period of periodic table contains total ……………. elements.

🟥A. 32

🟦B. 8 

🟩C. 18 ✅

🟨D. 2 

123. Which one of the following diffuses faster than oxygen with molar mass of 32 g/mol?

🟥A. Cl₂

🟦B. F₂

🟩C. SO₂

🟨D. N₂✅

124. Which one of the following substances contains covalent bonds but also conducts electricity?

🟥A. Copper

🟦B. Graphite✅

🟩C. Iron

🟨D. Sodium

125. Blood is one of the following:

🟥A. Element

🟦B. Compound

🟩C. Mixture✅

🟨D. Metal

126. Empirical formula of CH₃COOH is

🟥A.C₂H₄O₂

🟦B.CH₂O✅

🟩C.CH₄CO₂

🟨D.CHOC

127. Dobereiner arranged elements in

🟥A. Triads ✅

🟦B. Octaves

🟩C. Groups and periods 

🟨D. Sub-groups

128. Line spectrum of hydrogen was studied by

🟥A. Max Planck

🟦B. Albert Einstein

🟩C. Neil Bohr✅

🟨D. de Broglie

129. The radioactive element in VIIA group is

🟥A. Radium

🟦B. Francium

🟩C. Radon

🟨D. Astatine✅

130. The radioactive element in IA group is

🟥A. Rubidium

🟦B. Francium✅

🟩C. Cesium

🟨D. Potassium

131. It is considered as the fourth state of matter

🟥A. Gas

🟦B. Plasma✅

🟩C. Liquid

🟨D. Solid

132. This is the isotope of hydrogen which contains greater number of neutron:

🟥A. Protium

🟦B. Deuterium

🟩C. Tritium✅

🟨D. Hydrogen

133. Synthetic resin binds two surfaces together by this bonding

🟥A. Hydrogen bonding ✅

🟦B. Ionic bonding

🟩C. Covalent bonding 

🟨D. Metallic bond

134. Which one of the following is a polar compound?

🟥A. CH₄

🟦B. H₂S

🟩C. H₂O✅

🟨D. O₂

135. Noble gases are stable because their valence shell contains these number of electrons except helium

🟥A. 4 

🟦B. 6 

🟩C. 8 ✅

🟨D. 10 

136. All transition elements are

🟥A. Non-metals

🟦B. Metals✅

🟩C. Metalloids

🟨D. Gases

137. According to Avogadro’s law, one gram mole of any gas at STP occupies volume:

🟥A. 22.4 mm³

🟦B. 22.4 cm³

🟩C. 22.4 dm³ ✅

🟨D. 22.4 m³

138. Dry cell produces a potential of:

🟥A. 1.0 volt

🟦B. 1.5 volt✅

🟩C. 2.0 volt

🟨D. 12 volt

139. Leakage of helium gas through a gas balloon is an example of:

🟥A. Diffusion

🟦B. Effusion✅

🟩C. Evaporation

🟨D. Mobility

140. It is type of dipole-dipole interaction:

🟥A. Covalent bond

🟦B. Hydrogen bond✅

🟩C. Metallic bond

🟨D. Ionic bond

141. 5% m/m aqueous solution means that 5 g of solute is dissolved in:

🟥A. 90 g of water

🟦B. 95 g of water✅

🟩C. 100 g of water

🟨D. 105 g of water

142. The branch of chemistry that deals with the compounds in living organisms is called as:

🟥A. Analytical chemistry

🟦B. Biochemistry✅

🟩C. Organic chemistry

🟨D. Physical chemistry

143. Au is the chemical symbol for:

🟥A. Gold✅

🟦B. Silver

🟩C. Aluminium

🟨D. Argon

144. The symbol of silver is:

🟥A. Ag✅

🟦B. Au

🟩C. Si

🟨D. Sn

145. This atomic model is known as the quantum mechanical model of the atom:

🟥A. Schrodinger atomic model✅

🟦B. Rutherford atomic model

🟩C. Dalton’ atomic model

🟨D. Bohr’s atomic model

146. Which of the following gas diffuses faster?

🟥A. Oxygen

🟦B. Chlorine

🟩C. Fluorine

🟨D. Helium✅

147. Benzene is an example of this type of solvent:

🟥A. Polar

🟦B. Non-polar✅

🟩C. Ionic

🟨D. Universal

148. 69 g of sodium is equal to

🟥A. 1mole

🟦B. 2 moles

🟩C. 3 moles✅

🟨D. 4 moles

149. The size of particles in suspension is

🟥A. 10³ nm

🟦B. 10²nm

🟩C. Less than 10³ nm

🟨D. Greater than 10³ nm✅

150. 1 g equivalent weight of Ag is equal to

🟥A. 108 g✅

🟦B. 9g

🟩C. 27g

🟨D. 27g

151. This one is an alloy

🟥A. Graphite

🟦B. Steel✅

🟩C. Mercury 

🟨D. Water

152. This one of the following is non-electrolyte

🟥A. Molten KCl

🟦B. Urea✅

🟩C. Aqueous NaCl

🟨D. Aqueous HCl

153. This halogen exist in liquid state

🟥A. Fluorine

🟦B. Chlorine

🟩C. Bromine✅

🟨D. Iodine

154. This halogen exist in solid state

🟥A. Fluorine

🟦B. Chlorine

🟩C. Bromine

🟨D. Iodine✅

155. This element is a metalloid

🟥A. Br

🟦B. Si✅

🟩C. S

🟨D. Sr

156. This element is a metalloid

🟥A. B

🟦B. Ge

🟩C. As

🟨D. All of them✅

157. Natrium is the Latin name of this element:

🟥A. Nitrogen

🟦B. Neon

🟩C. Sodium✅

🟨D. Nickel

158. In chemical reaction ZnO + H₂ → Zn + H₂O, it is reduced:

🟥A. H

🟦B. H₂

🟩C. Zn✅

🟨D. O

159. CO₃²⁻ is a/an:

🟥A. Cation

🟦B. Anion✅

🟩C. Molecule

🟨D. Molecular ion

160. There are three sub-shells in

🟥A. N-shell

🟦B. M-shell✅

🟩C. L-shell

🟨D. K-shell

161. Boron is a:

🟥A. Metalloid✅

🟦B. Metal

🟩C. Non-metal

🟨D. Transition metal

162. Atomic radius is measured in:

🟥A. Yard

🟦B. Feet

🟩C. Inch

🟨D. Angstrom✅

163. This term would be the same for 1mole of oxygen gas and 1 mole of water?

🟥A. Atoms

🟦B. Mass

🟩C. Molecules✅ 

🟨D. Volume

🔥📘Answers of Section-B (Short-answer questions)

Q1. Define any three of the following:

Answer

Valency

Valency is defined as the number which expresses the combining or displacing tendency of an element with other elements and it is the number of electrons lost or gained or shared by an atom of the element during a chemical reaction in order to complete its outermost shell (Octet).

Electronegativity

The relative ability or power of an atom in a molecule to attract a shared pair of electrons towards itself is called electronegativity. Electronegativity is dimensionless quantity i.e. it has no unit.

Electron affinity

Affinity means attraction, therefore, electron affinity means tendency to accept electron to form anion. The amount of energy released when an electron is added in the outermost shell of a gaseous atom is called electron affinity denoted as E.A. It is expressed in kJ/mol.

Tyndall effect

The scattering of visible light by Colloidal particles is called Tyndall effect discovered by Physicist John Tyndall.

Free radical

Free radicals are atoms and group of atoms having number of unpaired electrons. For example CH₄⁺

Molecular ion

when a molecule loses or gains electrons is called molecular ions. For example Ho, CH₃o

Mole

Mole is the S.I. base unit of chemical amount of substance. A mole of a substance can be defined as the atomic mass or molecular mass or formula mass of a substance (element or compound) expressed in gram containing 6.02 x 10²³ particles (Atoms, molecules or ions). A mole is defined as “amount of substance containing equal to the Avogadro’s number 6.02 x 10²³.

Molar volume

The volume occupied by one mole of any gas at s.t.p is 22.4 dm³
 (Litre) and is referred to as Molar Volume.

1 mole of a gas at S.T.P = 22.4 dm³ mol⁻¹

Empirical formula

It is the type of formula which expresses only the minimum relative numbers of each type of atoms in a molecule of a compound. E.F of a compound is determined by experimental analysis. Empirical Formula tells us the type of element present in it.

Molecular formula

It is the type of formula which expresses the actual number of atoms of each element present in a molecule of a substance. Molecular formula is same as empirical formula or it may be an integral multiple of empirical formula.

Molarity

Molarity is defined as the number of moles of solute dissolved per 1 dm³ (1 liter) of a solution denoted by M.

Concentration

The proportion of solute in a solution is called concentration. The concentration (strength) of a solution is the ratio of amount (mass or volume) of the solute present in known amount of solvent or solution.

False solution

A homogenous mixture in which solute particles are larger than those present in the true solution but not large enough to be seen by naked eyes are called false solution or colloidal solution.

Mass by volume percent (%m/v)

It is the mass of the solute in grams dissolved per 100cm3 of the solution.

Freezing Point

The temperature at which the vapour pressure of a liquid state becomes equal to the vapour pressure of its solid state is known as Freezing Point of a liquid. At this temperature liquid and solid coexist in dynamic equilibrium.

Absolute zero

It is the temperature at which an ideal gas would have zero volume. It is equal to –273°C.

Allotropy

The existence of an element in more than one crystalline forms is known as allotropy. These forms of the element are called allotropes or allotropic forms.

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

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:

Answer

Atomic Number

The number of protons present in the nucleus of an atom of an element is called atomic number (Z).

Mass Number

The sum of number of protons and neutrons of an atom is called mass number (A).

Isotopes

Isotopes are atoms of the same element having SAME ATOMIC NUMBER (OR SAME NUMBER OF PROTONS (and also electrons) but DIFFERENT MASS NUMBERS or atomic masses (or DIFFERENT NUMBER OF NEUTRONS)”. (Different isotopes of an element display the same chemical properties due to their identical electronic configuration but they have different physical properties because of their different atomic masses).

Applications of Isotopes

Isotopes of Hydrogen

There are three isotopes of hydrogen namely protium or ordinary hydrogen, deuterium or heavy hydrogen, tritium or radioactive hydrogen.

Isotopes of Carbon

There are two stable isotopes and one radioactive isotope of carbon. The carbon-12 contain 6 proton and 6 neutron, Carbon-13 possess 6 proton and 7 neutron, carbon-14 contain 6 proton and 8 neutron. Carbon 12 is the most abundant (98.889%) isotope.

Isotopes of Uranium

There are three common isotopes of uranium with atomic number 92 and mass number 234, 235 and 238 respectively. The uranium is found 99% in nature.

4. 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

Answer

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

5. Compare of reactivity of Alkali and Alkaline Earth Metals

Answer

OR

Write down one contribution of any 10 scientists in the field of chemistry.

Answer

OR

Explain the importance of glues and epoxy resins in our society.

Answer

Synthetic adhesives like epoxy resins and glues are the substance that stick to the surface of the other objects.

Epoxy glue contains epoxy. Its form strong bonds with glass, plastics, plywood, laminated boards and ceramic. Another use for epoxy resin is the decorative flooring applications. Commonly, epoxy resins are used where water resistance is required. Bridges, dams, power stations are also coated with epoxy resins.

Explain how Aircrafts, cars, trucks and boats parts are partially held together with epoxy adhesive

The excellent adhesive properties of epoxy resins are due to the attractive forces between the epoxy resin and the surface of the substrate. One of the most common uses of epoxy resin is for adhesive purposes. For that purpose, epoxy resin is used in the construction of vehicles, trucks, boats and aircrafts. Its drying time is 6-30 minutes hardly.

Answer

Sand ………………..….. SiO₂

Lime stone ………….. 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.

Answer

Definition and Representation

It is a special type of covalent bond which is proposed by Sidgwick who named it as Dative Bond.

The type of bond in which bond pair of electrons is contributed by one atom only, is called coordinate covalent or dative covalent bond.

Examples

1. Formation of Ammonium Chloride by the Reaction between Ammonia and Hydrogen Chloride

The reaction between ammonia and hydrogen chloride involves the formation of a dative bond between N atom in NH3 containing lone pairs and H+ ion from HCl. When ammonia reacts with hydrogen ions (H+) in an aqueous solution of an acid, the hydrogen ion is attracted to the lone pair and a coordinate covalent bond is formed.

2. Formation of Oxonium/Hydronium Ion

In the formation of oxonium or hydronium ion (H3O+) from water molecule and hydrogen ion or proton, H+ (released by acid like HCl in aqueous solution), the oxygen atom of water donates its lone pair to hydrogen ion, H+ for one-sided sharing to make co-ordinate covalent bond.

Q7. Write down any three points of atomic model proposed by Schrodinger or Bohr.

Answer

In 1926 Erwin Schrödinger, an Austrian physicist, Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. He found electrons are in orbit as an electron cloud.

Basic Postulates

1. electron can be found in various location around the nucleus as a fuzzy electron cloud. The place where the probability of finding an electron within certain volume of space surrounding the nucleus is maximum and electron cloud is denser is called atomic orbital.

2. Each energy subshell in an orbit has different shapes which determine the presence of electron.

3. Different subshells or orbitals are named as s, p, d and f with different shapes. e.g. s-orbital is spherical and p-orbital is dumbbell shaped.

4. The numbers and kind of atomic orbitals depends on the energy subshell.

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.

Answer

In 1923 Lois de Broglie extend the wave particle duality to electron, and propose a hypothesis that all matter has particle as well as wave nature at the submicroscopic level. de Broglie combined the Einstein and Planck equations to derive its de-Broglie’ equation. The wave nature of a particle is quantified by de Broglie wavelength defined as λ = h/p where p is the momentum of the particle.

All matter (material) particles in motion have a dual character exhibiting both particle and wave nature i.e. electrons, protons, neutrons, atoms, and molecules possess the characteristics of both the material particle and a wave. This is called wave-particle Duality in matter.

de-Broglie derived a mathematical equation known as de-Broglie’s equation which relates the wavelength (λ) of the material particle (electron) of mass m moving with velocity v to its momentum (mv = p):

λ = h/mv or λ = h/p

Proof

E = hν [According to Planck’s equation]

And

E = mc² [According to Einstein’s mass-energy equation]

hu = mc² [By equating the two energies]

But

ν = c/ λ [∵ c = h/ λ]

hc/ λ = mc²

h/ λ = mc²/c

h/ λ = mc

λ = h/mc

Considering that nature is symmetrical, we apply this equation to the moving electron of mass m thereby deriving de-Broglie’s equation and velocity.

λ = h/mv [de-Broglie’s equation]

OR

OR

Justify that Rutherford atomic model has defects? What are Limitations of Bohr's Atomic Model?

Answer

Justification of Rutherford Atomic Model has Defects

Neil Bohr pointed out some serious defects in Rutherford’s Atomic Model:

1. Rutherford did not explain the stability of an atom.

2. According to the Classical Physics, since electron is revolving around the nucleus constantly it should lose energy continuously and it ultimately falls into the nucleus.

3. If the revolving electron continuously emits energy, then there would be a continuous spectrum but in contrast to, a line spectrum is obtained from the atoms of elements.

Limitations of Bohr’s Atomic Model

1. It failed to explain the Zeeman Effect (effect of magnetic field on the spectra of atoms).

2. It also failed to explain the Stark effect (effect of electric field on the spectra of atoms).

3. It is against the Heisenberg Uncertainty Principle.

4. It could not explain the spectra obtained from larger atoms.

5. It explained the mono-electronic species like H⁺, Li²⁺, B³⁺.

Prediction of Nature of Bond Using Electronegativity

The electronegativity values help to decide the nature of bond between two atoms.

1. if the difference in the electronegativities of bonded atoms is more than 1.7, then the bond is ionic.

2. if the difference in the electronegativities of bonded atoms is less than 1.7, then the bond is covalent

3. If the difference in electronegativities is zero or less than 0.5, then the bond is pure covalent or non-polar covalent bond. e.g. H–H, O=O, N≡N, NCl₃, CH₄, F–F, Cl–Cl, I–I, Br–Br, etc.

4. If the difference in electronegativities is more than 0.5 but less than 1.7, then the bond is polar covalent or partially ionic in character e.g. H – F, H – Cl, H – O – H etc.).

If ΔE.N. > 1.7 –––– bond will be ionic.

If ΔE.N. < 1.7 –––– bond will be covalent.

If ΔE.N. > 0.5 < 1.7 –––– bond will be polar covalent or partially ionic.

If ΔE.N. = 0 or < 0.5 –––– bond will be non-polar or pure covalent.

Ionic Character of Covalent Bond

Polar covalent bond has some amount of ionic character or polarity. Thus it is not a pure covalent bond and has partial ionic character. A polar bond containing molecule acts as dipole.

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

5. Pure solids have sharp melting point.

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.

Answer

Diffusion

The spontaneous mixing of molecules by random motion and collision to form a homogenous mixture is called diffusion. Diffusion is movement of particles from an area of high concentration to one of low concentration. Diffusion results in the gradual mixing of materials, and eventually it forms a homogeneous mixture.

Reason of Rapid diffusion in gases

Gases are rapidly diffusible due to free movement of molecules.

Graham’s law of diffusion of gases

The quantitative relationship between the rate of diffusion of different gases and their molar masses or densities is called Graham’s Law of Diffusion established by a Scottish chemist, Thomas Graham in 1846. This law states that:

“The rate of diffusion of a gas is inversely proportional to the square root of its density or molar mass (under the same conditions of temperature and pressure).”

Reason of diffusion

According to Graham’s law, lighter gases diffuse faster than heavier gases. e.g. among CO₂, CH₄ and H₂, H₂ gas has least molar mass so it diffuses fastest while CO₂ has highest molar mass so it diffuses slowest. CH₄ has moderate molar mass so it diffuses slowly than H₂ but quickly than CO₂. The increasing order of rate of diffusion is

CO₂ < CH₄ < H₂

Q11. Differentiate between amorphous and Crystalline Solids?

OR

Explain the solute-solvent interaction to prepare sodium chloride solution.

Answer

Comparison between crystalline and amorphous solids

OR

Explain the solute-solvent interaction to prepare sodium chloride solution.

Answer

In order to dissolve the solute into solvent, the following conditions must be fulfilled.

(i) Solute-Solute bonding should be broken.

(ii) Solvent-Solvent bonding should be broken to provide space for solute particles.

(iii) Solute-Solvent attraction should be maximized.

When solute-solute or solvent-solvent interactions are much more than solute-solvent interaction, a solution will not form.

The process of solution formation depends upon the relative strength of attractive forces between solute-solute, solvent-solvent and solute-solvent. A solute will dissolve in a solvent if the solute-solvent forces of attraction are greater enough to overcome the solute-solute and solvent-solvent forces of attraction. A solute will not dissolve if the solute-solvent forces of attraction are weaker than individual solute and solvent intermolecular attractions.

As we know that sodium chloride is an ionic compound. When sodium chloride (NaCl) is placed in water, it dissolves quickly. The negative end of water molecules is attracted to sodium ions and the positive end of water molecules is attracted to chlorine ions. In this case, solute-solvent attractions are more in comparison with solute-solute interaction, therefore solution of sodium chloride is formed. These attractive forces of water are stronger enough to overcome the attraction between Na⁺ and Cl⁻ ions in NaCl. The following figure shows the attraction of Na⁺ and Cl⁻ ions with water molecules.

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

Answer

Electrochemical reactions

The chemical reactions in which chemical energy changes into electrical energy or vice versa are called electrochemical reactions. Oxidation and reduction reactions are electrochemical reactions.

Redox Reaction

Redox reactions are electrochemical reactions which involve simultaneous oxidation and reduction.

Identification of OA and RA in given Reaction

Zn (RA, oxidizes) + Cl₂ (OA; reduces) → 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)

Answer

Difference between Electrolytes and Non-electrolytes

Identification of strong and 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?

Answer

Definition of Corrosion

Metals react with oxygen in presence of moisture and can form harmful metal oxide. These metal oxide layers are porous and expose metal for further reaction with oxygen to form harmful metal oxide. It is called Corrosion of metal.

Rusting of Iron

Corrosion of iron is called rusting which an electrochemical process. Iron undergoes redox reaction in presence of air or water to form iron (III) oxide (Fe₂O₃.nH₂O) called rusting of iron. Rusted surface of iron provide no protection to underlying iron and eventually convert whole iron into reddish brown rust. Rusting occurs at different places of metal surface. A metal surface area of less moisture acts as anode and oxidizes iron in this region. Metal surface with high moisture contents acts as a cathode and reduces atmospheric oxygen to OH⁻ ions The Fe²⁺ ions further reacts with oxygen to form rust, iron(III) oxide (Fe₂O₃.nH₂O)

Fe(s) → Fe²⁺(aq) + 2ē ………… (Oxidation

O₂ + 2H₂O + 4ē → 4OH⁻ (aq) ………… (Reduction)

Prevention from corrosion

All metals can be prevented from corrosion by following methods.

1. Alloying

Formation of alloy prevents metal from corrosion by reducing its ability of oxidation.

Example: Iron (Fe) can be changed into stainless steel by mixing with chromium (Cr) and Nickel (Ni). Thus iron (Fe) is prevented from corrosion.

2. Metallic Coating (Electroplating)

All metals can be protected from corrosion by coating its surface with other metal like tin (Sn) or zinc (Zn). The coating of metal at the surface of other metal by electrolytic process is called electroplating. Metals like iron can be electroplated with chromium (Cr), Nickel (Ni) and silver (Ag).

3. Cathodic Protection

It is applied to protect underground pipes tanks, oil rigs etc. from corrosion by making these materials as cathode. The active metal like magnesium (Mg) or aluminum (Al) is used as Anode and connected with iron (Fe). These active metals itself oxidizes and prevent other metal from corrosion.

4. Coating with paint

A metal is commonly coated with paint to protect it from corrosion. Paint prevents the reaction of metal with oxygen, moisture and other harmful chemical agents.

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)

Answer

Q14. What are metalloids? Write names and symbols of any 5 metalloids.

Answer

Definition

Metalloids are the elements which exhibit dual character and have characteristics of both metals as well as non-metals. i.e. have a blend of metal and non-metal properties. Their oxides are amphoteric showing acidic as well as basic nature.

Many metalloids show intermediate properties between the metals and non-metals. Some of the metalloids are semi-conductors like silicon, germanium and boron.

Position of metalloids in the periodic table

Metalloids are found along stair-step (staircase) line or diagonal boundary between metals and non-metals from B to Al to the border between Po and At (the only exception to this is Al which is classified under “weak or other metal’).

Examples of Metalloids

There are total 8 metalloids:

1. Boron of group IIIA

2. Silicon and germanium of group IVA

3. Arsenic and antimony of group VA

4. Tellurium and polonium of group VIA

5. Astatine of group VIIA

OR

Write names and symbols of some noble metals. Explain inertness of noble metals.

Answer

Noble metals include Gold (Au-79), Silver (Ag-47), Platinum (Pt-78), Iridium (Ir-77), Osmium (Os-76), Rhodium (Rh-45), Ruthenium (Ru-44), Palladium (Pd-46).

Reason of Inertness of Noble Metals

The inertness of noble metals is due to their less electropositivity. Hence they are difficult to oxidize. Therefore they show no reaction with atmospheric gases and resist corrosion. This helps noble metals to maintain their appearance so noble metals like Ag, Au, Pt are used to make ornaments.

OR

Define Moh Scale. What are Soft and Hard Metals? Differentiate between sodium and iron as soft and hard metal.

Answer

Soft and Hard Metals and Moh Scale

The hardness of metal is the resistance of metal to be scratched. Hardness of metals and other material is measured by Moh scale which is based on scratch resistance of different metals and other materials. It is devised by Frederich Mohs in 1812. Metals may be soft or hard. Hardness of plastic, Lead pencil is 1, and that of Diamond is 10 on Moh scale.

Metal …………………………… Li     Na     K     Rb   Cs   Ni   Fe    W

Hardness on Moh Scale ……….. 0.8    0.5    0.4  0.3  0.2   4   4.5  7.5

The metals which are scratched easily are called soft metals. Alkali metals like; Sodium (Na), Potassium (K) and Rubidium (Rb) are soft metals.

Metals which show strong resistance towards scratching are called hard metals. Nickel (Ni), Iron (Fe), Tungsten (W) are hard metals.

Difference between Na and Fe as soft and hard metal

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?

Answer

Boiling Point

The temperature at which vapour pressure of a liquid become equal to atmospheric pressure is called boiling point of the liquid.

Factors affecting Boiling Point

(i) Atmospheric Pressure

The boiling point is directly proportional to atmospheric pressure. Boiling point can be increased by increasing atmospheric pressure. For example working of pressure is based on this fact.

(ii) Nature of Liquids

The boiling point depends upon the nature of liquid. Polar liquids with stronger intermolecular forces have high boiling point than non-polar liquids with weak intermolecular forces.

(iii) Intermolecular forces

Boiling point is directly proportional to strength of intermolecular forces. Liquids having stronger intermolecular forces have high boiling points because such liquids attain a level of vapour pressure equal to external pressure at high temperature.

19. 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) Covalent bonds are strong and hard to break but why most of the covalent compounds have low melting and boiling points.

Answer

(i) Why gasoline does not dissolve in water?

Answer

The general, principle of solubility is “Like dissolves like”. polar or ionic solutes easily dissolve in polar solvents whereas non-polar solutes easily dissolve in non-polar solvents and hence it is said that like dissolves like. Gasoline is a mixture of hydrocarbons heptane and octane being non-polar does not dissolve in polar solvent water.

(ii) Alkali metals are not found in free state in nature, why?

Answer

Due to their low ionization enthalpy values, all alkali metals readily lose their single valence electron and are highly reactive. Therefore, alkali metals are never found in nature in free (uncombined or native or elemental ) state. In combined state, they are present in the form of halides, oxides, silicates, borates and nitrates.

(iii) Why ionic compounds conduct electricity in molten or in aqueous solutions only?

Answer

Aqueous solutions of ionic compounds also conduct electricity. This is because when an ionic compound dissolves in water, the ions are free to move in aqueous solution.

They do not conduct electricity in the solid state as the ions are not free to move. But they are good conductor of electricity in molten state or in solution form due to free movement of the ions.

(iv) Why the solubility of a salt increases with the increase in temperature?

Answer

Solubility is directly proportional to the temperature in solid & liquid. The solubility of solids in liquids usually increases with the rise in temperature because hot water molecules have greater kinetic energy and collide with solid solute more vigorously.

For example;

a greater amount of sugar will dissolve in warm water than in cold water. (solubility of sugar in water at 0°C is 179 g/100 ml of water whereas 100°C it is 487 g/100 ml of water).

(v) Explain why table salt has a very high melting point.

Answer

Sodium chloride is an example of ionic or electrovalent compound having strong ionic bonding in the form of strong electrostatic force of attraction between the oppositely charged sodium and chloride ions. Hence it requires more heat energy to overcome the strong electrostatic attraction between its positive and negative ions resulting in its high melting point.

(v) Covalent bonds are strong and hard to break but why most of the covalent compounds have low melting and boiling points.

Answer

Covalent compounds have generally low melting points because they are made up of electrically neutral molecules having weak force of attraction in the form intermolecular forces. Hence, only a small amount of heat energy is required to break these weak intermolecular forces.

🌈🔥Solutions of Important Numericals

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

Q2. What is the mass of oxalic acid (C₂H₂O₄) required to prepare 100 cm³ volume of 2M oxalic acid solution?

Solution

Given Data

Molarity of solution = 2 M or mol/dm³

Volume of solution = 100 cm³ ⇒ 100 / 1000 = 0.1 dm³

Molar mass of H₂C₂O₄ = 2(1)+ 2 (12) + 4(16) = 90 g/mol

Required

Mass of solute (H₂C₂O₄) = ?

Formula

Mass of solute in g = Molarity x Molar mass of solute x Volume of solution in dm³

Calculation

Mass of H₂C₂O₄ in gram = 2 x 90 x 0.1

Mass of H₂C₂O₄ in gram = 18 g

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

Given

Mass of solute; HCl = 1.25 g

Volume of solution = 30 cm³ ⇒ 30/1000 = 0.03 dm³

Molar mass of HCl = 1 + 35.5 = 36.5 g/mol

Required

Molarity (M) of HCl solution =?

Formula

Calculation

Q3. 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?

Solution

Given

P₁ = 750 mm of Hg

V₁ = 800 cm³

V₂ = 250 cm³

Required

P₂ = ? 

Parent Formula and Calculation

P₁V₁ = P₂V₂ ⇒ P₂ = P₁V₁/ V₂

P₂ = 750 (mm Hg) x 800 (cm³)/ 250 (cm³)

P₂ = 2400 mm Hg

Result

The decrease in volume increases the pressure.

OR

Q4. Determine the percentage concentration of the solution obtained by dissolving 10g sugar in 140g water

Solution

Mass of solute (sugar) = 10 g

Mass of solvent (water) = 140 g

Mass of solution = mass of solute + mass of solvent = 10 + 140 = 150 g

Mass % of sugar = ?

Thus the concentration of a solution is 6.66% by mass.

OR

Q. A solution of 20 cm³ of alcohol is dissolved in 80cm³ of water. Calculate the concentration (v/v) of this solution.

Solution

Volume of solute (ethanol) = 20 cm³

Volume of solution = 150 cm³

Volume/volume percent = ?

Q5. 10M HNO₃ solution is available in laboratory. How would you prepare 500 cm³ of 0.1M solution?

Solution

M₁ = 10M

V₂ = 500cm³

M₂ = 0.1 M

V₁ = ?

Formula

Calculation

10 x V₁ = 0.1 x 500

V₁ = 0.1 x 500/10

V₁ = 5 cm³

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 H₂
SO₄? (Answer; 12.5cm³)

Solution

M₁ = 20M

V₂ = 500cm³

M₂ = 0.5 M

V₁ = ?

Formula

Calculation

20 x V₁ = 0.5 x 500

V₁ = 0.5 x 500/20

V₁ = 12.5 cm³