Get the X-Chemistry National Comprehensive Targeted Guess Paper 2026 for Class 10 Chemistry. Designed specially for Karachi Board students, this paper includes important MCQs, short questions, and long questions expected in the final exams 2026. Prepare smartly and score high with updated Karachi Board notes and exam tips!
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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 4 are to be answered (24marks)
🔥📘 Section-A ……….. MCQs (Compulsory question)
(12 marks) Model Set I
1️⃣. For the reaction 2A(g) + B(g) ⇌ 3C(g), the equilibrium constant expression is:
🟩 A. [2A][B]/[3C]
🟪 B. [A]²[B]/[C]³
🟨 C. [3C]/[2A][B]
🟦 D. [C]³/[A]²[B]✔️
2️⃣. Equilibrium constant value “Kc“ is equal to:
🟩 A. Qc/Kr
🟪 B. Kr/Kf
🟨 C. Kc/Qc
🟦 D. Kf/Kr✔️
3️⃣. NH₃ can be a base according to:
🟩 A. Arrhenius theory
🟪 B. Bronsted-Lowry theory
🟨 C. Lewis theory
🟦 D. both b and c✔️
4️⃣. Which of the following is a Lewis base?
🟩 A. HNO₃
🟪 B. AlCl₃
🟨 C. HCl
🟦 D. CN⁻✔️
5️⃣. The general formula of alkynes is:
🟩 A. CₙH₂ₙ
🟪 B. CₙH₂ₙ₊₁
🟨 C. CₙH₂ₙ₋₂✔️
🟦 D. CₙH₂ₙ₊₂
6️⃣. Which of the following is an alcohol?
🟩 A. CH₃CHO
🟪 B. CH₃CH₂OCH₃
🟨 C. CH₃CH₂OH✔️
🟦 D. HCOOH
7️⃣. Which one of the following is a polysaccharide?
🟩 A. Fructose
🟪 B. Maltose
🟨 C. Starch✔️
🟦 D. None
8️⃣. Cellulose content in cotton is:
🟩 A. 70%
🟪 B. 95%✔️
🟨 C. 85%
🟦 D. 90%
9️⃣. Ozone layer is part of the:
🟩 A. Stratosphere✔️
🟪 B. Mesosphere
🟨 C. Thermosphere
🟦 D. Troposphere
🔟It is Used to assess concentration of atomic/molecular/ionic species:
🟩 A. Chromatography
🟪 B. Spectroscopy✔️
🟨 C. Conductometry
🟦 D. Potentiometry
1️⃣1️⃣. Surfactants reduce the ______ of water.
🟩 A. Surface tension✔️
🟪 B. Viscosity
🟨 C. Boiling point
🟦 D. Melting point
1️⃣2️⃣. The centrifuge machine is used for separation of:
🟩 A. Crystals✔️
🟪 B. pH
🟨 C. Mud
🟦 D. Juice
1️⃣3️⃣. Insulin is basically a:
🟩 A. Enzyme
🟪 B. Hormone✔️
🟨 C. Starch
🟦 D. Mineral
1️⃣4️⃣. Vital force theory was introduced by:
🟩 A. Robert Boyle
🟪 B. J. J. Berzelius✔️
🟨 C. Lewis
🟦 D. Wohler
1️⃣5️⃣. Lactose enzymes are used:
🟩 A. In production of bread
🟪 B. To make ice cream sweeter✔️
🟨 C. To make alcohol
🟦 D. To maintain colour
✅ Answer Key with Short Reasons
1️⃣D — Products over reactants, coefficients become powers.
2️⃣D — Kc = Kf/Kr (ratio of forward and reverse rate constants).
3️⃣D — NH₃ accepts a proton (Bronsted) and donates lone pair (Lewis).
4️⃣D — CN⁻ has lone pairs → Lewis base.
5️⃣C — Alkynes general formula is CₙH₂ₙ₋₂.
6️⃣C — CH₃CH₂OH is ethanol (an alcohol).
7️⃣C — Starch is a polysaccharide.
8️⃣B — Cotton contains about 95% cellulose.
9️⃣A — Ozone layer lies in the stratosphere.
🔟B — Spectroscopy measures concentration via light interaction.
1️⃣1️⃣A — Surfactants lower surface tension.
1️⃣2️⃣A — Centrifugation separates crystals.
1️⃣3️⃣B — Insulin is a hormone.
1️⃣4️⃣B — Wohler disproved vital force, but Berzelius proposed it;
1️⃣5️⃣B — Lactase breaks lactose into sweeter sugars in ice cream.
1. Define any three of the following:
equilibrium constant, reaction quotient, extent of a reaction, pH, Indicator, Neutralization, Titration, alicyclic compounds, aromatic compounds, catenation, aldoses, ketoses, saccharides, functional group, Peptide linkage, saponification, lipids, enzymes, isomerism, Bloor’s reagent, fatty acid, ozone hole, organic chemistry, Biochemistry, Environmental chemistry, Analytical Chemistry, Qualitative Analysis, Quantitative Analysis, accuracy, precision, titrant, analyte, Indicator, parameter
2. Write down three differences between any one of the following:
(i) Troposphere and Stratosphere(ii) reversible and irreversible reactions
(iii) saturated and unsaturated hydrocarbons
(iv) Dextrorotary and Levorotatory Sugars
(v) Quantitative analysis and qualitative analysis
(vi) Titrimetric analysis and gravimetric analysis
(vii) Classical and Instrumental Methods
(viii) fat and water-soluble vitamins.
(ix) DNA and RNA
(x) fat and oil
(xi) Aldoses and ketoses
3. Define chemical equilibrium
state. Why chemical equilibrium is dynamic? Explain it with one example.
OR
Describe the characteristics of equilibrium constant. Why equilibrium constant may or may not have unit? Justify with example.
4. Write down Equilibrium Constant Expression (Kc) and unit of Kc for any 3 of the following balanced reversible reactions.
(i) N2(g) + 2O2(g) ⇌ 2NO2(g)
(ii) H2(g) + I2(g) ⇌ 2HI(g)
(iii) CO2(g) + H2(g) ⇌ CO(g) + H2O(g)
(iv) 2SO2(g) + O2(g) ⇌ 2SO3(g)
(v) N2(g) + 3H2(g) ⇌ 2NH3(g)
(vi) CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g)
6. State vital force theory and how was this
theory discarded by Wohler?
Or
Write the names and structural formulae of
six carbons alkanes, alkenes, alkyne, cycloalkane and aromatic hydrocarbons.
OR
Draw the
structures of following compounds:
(i) 2,3-dimethylpentane
(ii) 3-ethyl-1-hexene
(iii) 2-butyne
(iv)
2,4-hexadiene
(v) 3-methyl-1,4-hexadiyne
(vi) 2-hepten-5-yen
(vii) 2-pentyne
(viii) neopentane
(ix) iso-propyl alcohol
(x) Phenol or toluene
(xi) iso-butane
(xii) Cyclohexane
8. Define salt
and its three types with two examples each. Give three uses of salts. Also
write any three methods of
preparation of salts with equation.
OR Write
one use of enzymes yeast, cellulase and amylase.
OR What is homologous series? Name the any two
common homologous series with examples. Write down the general characteristics of homologous series.
OR
What
is alkyl radicals? Give its type formula and general formula. Explain with
structure different radicals of butane.
What is the difference of alkyl radicals obtained from propane?
9. Elaborate
ionization equation of water. Explain in detail that how water ionization is
related with pH of solution?
OR
Define buffers. What is the composition of buffers? Discuss its importance in our daily life.
10. Write any
three significant uses of Carbohydrates and lipids.
OR
What are amino acids and peptide bond? How peptide bond is formed? Also explain dipeptides & tripeptides.
11. Give
reason:
(i) Why Silicon compounds are lesser than that of Carbon compounds?
(ii) Why pure water is considered as weak electrolyte?
(iii) Justify the petroleum is ‘black gold’.
(iv) Alkanes are said to be saturated hydrocarbons.
(v) Justify that water soluble vitamins are not injurious to health.
(vi) Justify that greenhouse effect leads to global warming
(vii) Justify that “water is solvent”.
(viii) How is vegetable oil is converted into saturated fat (ghee)?
(ix) Why chemical equilibrium is considered dynamic not static?
(x) Why the temperature on top of a mountain is colder than at sea level?
13. What
are Oligosaccharides, Disaccharides and polysaccharides. Give their examples
and sources.
OR
What are the carbohydrates? Explain sources and types of carbohydrates.
14. What are
amino acids and give their general structure? How many Essential and
Non-essential Amino acids are there? Write down the range of Number
of Amino acids and molecular
weights of Proteins
OR
What are fatty acids? Give their examples and chemical nature.
15. Briefly describe any three beneficial impacts of pharmaceutical industry on human society.
16. Write down causes of following
diseases:
(i) Diarrheal Diseases
(ii) Dysentery
(iii) Cholera
(iv) Crytosporidium
(v) Fluorosis
(vi) Hepatitis
(vii) Hookworm
(viii) Typhoid
17. What is
the cause of acid rain? Explain. Write down the effects of acid rain and global
warming.
OR
What are primary and secondary air pollutants? Or Give difference between primary and secondary air pollutants. Identify as primary or secondary air pollutant SO2, CH4, HNO3, NH3, H2SO4 and O3
18. Describe the composition of water. Write degree of Hardness of water on the basis of Dissolved Ca Ions (mg/L)
19. List down
the applications of conductometry?
OR
Describe the composition of water. Write down degree of Hardness of water on the basis of Dissolved Ca Ions.
20. What is error? Write down causes of errors with their %. Write down brief note systematic and random errors with two examples each.
OR
Describe fractional distillation of petroleum with its 5 fractions.
21. A solution of HCl has pH of 2.3.
Calculate its pOH and [H+]?
OR
Find pH, pOH, [OH−] and [H+] of 2.46 × 10−9 M KOH solution.
22. State law of mass action and define Kc. Derive an expression for equilibrium constant for a general reaction.
23. State and explain
Bronsted-Lowry acid-base theory or Lewis concept of acids and bases with
examples? explain with an example that water is a Bronsted-Lowry
acid as well as Bronsted-Lowry base. OR
State three different theories about concepts of acids and
bases with one example and also indicate one limitation
of each concept. Which of the following is/are Arrhenius acids and bases?
(a) Ca(OH)2 (b) HNO3 (c) NaOH (d) H2SO4 (e) KOH
24. Define
functional group. Write different functional groups which contain carbon,
hydrogen and oxygen.
OR
Define nomenclature and describe IUPAC nomenclature rules for alkynes and alkanes. Write down IUPAC names of following:
25. What are the
main sources of organic compounds? Mention with special reference of coal,
petroleum and natural gas.
OR
What do you mean by diversity and magnitude of organic compounds? Give at least 5 reasons.
26. What are Lipids?
Write down the sources and
uses of lipids. Write five
differences between Fats and Oils.
OR
What are proteins and peptide bond? How peptide bond is formed in dipeptides and tripeptides ? Write down the range of Number of Amino acids and molecular weights of Proteins. Give importance and sources of proteins.
27. Describe in detail nucleic acids, RNA and DNA. Write down importance of deoxyribonucleic acid (DNA).
28. Describe process of Saponification with the help of
flow sheet diagram.
OR
Describe fractions of petroleum in detail.
29. Justify that electrochemical methods depend upon electrochemical
cells.
OR What is Titrimetric Analysis? Describe how it is performed with diagram.
30. Explain the process of preparation sugar from sugar cane. OR Describe process of Saponification with the help of flow sheet diagram.
31. What is Ozone? How does Ozone depletion occur by
Chlorofluorocarbons (CFCs) also mention some adverse impact of it?
OR Describe global warming. Justify that greenhouse effect leads to global warming.
32. Describe Gas Chromatography with diagram also write two uses of gas chromatography.
33. What are Soft Water and Hard Water and describe different methods of removing temporary and permanent hardness. Write down 5 disadvantages of hard water.
34. Definition Water Pollution. Write down its Causes and Effects on Life
35. For
the reaction, H2(g) + I2(g)
⇌ 2HI(g) (Kc = 57.0); the
concentrations of H2(g), I2(g) and HI(g) at
time t are:
[H2]t = 0.10 mol dm−3,
[I2]t = 0.20 mol dm−3,
[HI]t = 0.40 mol dm−3
Predict in which direction reaction will move
to achieve equilibrium.
(Answer; Qc (8.0) is less than Kc (57.0), reaction will move in the forward direction)
OR
Equilibrium
occurs when nitrogen monoxide gas reacts with oxygen gas to form nitrogen
dioxide gas
2NO(g) + O2(g) ⇌ 2NO2(g)
At equilibrium at 230oC, the concentrations are
measured to be
[NO] = 0.0542 mol dm−3,
[O2] = 0.127 mol dm−3
and
[NO2] = 15.5 mol dm−3
Calculate the equilibrium constant at this temperature. (Book problem 1; page 8)(Answer; 6.44 x 105 mol-1 dm3)
🧪📚 Answers of Section-B (Short-Answer Questions)
1. Define any three of the following:
Active mass, Equilibrium constant, reaction quotient, extent of a reaction, pH, Indicator, Neutralization, Titration, alicyclic compounds, aromatic compounds, catenation, aldoses, ketoses, saccharides, functional group, Peptide linkage, Saponification, lipids, enzymes, isomerism, Bloor’s reagent, fatty acid, ozone hole, organic chemistry, Biochemistry, Environmental chemistry, Analytical Chemistry, Qualitative Analysis, Quantitative Analysis, accuracy, precision, titrant, analyte, Indicator, parameter
Answer
Active Mass
The Molar Concentration in mol/dm³ or mol dm⁻³ (mol/litre) of substances is termed as ACTIVE MASS which represented by square brackets; [ ].
Equilibrium Constant (Kc)
The equilibrium constant (Kc) of a reversible reaction is a constant ratio of Kf/Kr (specific rate constant for forward reaction/specific rate constant for reverse reaction) at constant temperature. Equilibrium constant is a ratio of the product of the equilibrium molar concentrations (active masses) of products to the product of the equilibrium molar concentrations (active masses) of reactants with each concentration term raised to the power of coefficient as expressed in the balanced chemical equation at constant temperature.
Reaction Quotient (Q or Qc)
It is the ratio of initial concentration of products and initial concentration of reactants (not necessarily at equilibrium).
Extent of a reaction
The extent of reaction is the limit up to which reactants are changed to products. It indicates to which extent reactants are converted to products.
pH
pH is a measurement of the concentration of hydrogen ions (H⁺) in a solution. pH is an abbreviation for power of H⁺ ion concentration. pH of a solution is defined as the negative logarithm of the molar hydrogen ions concentration [H⁺] (in mol/litre) of a solution. pH values range from 0-14.
pH = – log [H⁺]
Indicators
Indicators are complex the weak organic acids or bases which change colour over small range of pH in acidic or basic medium and by means of it end-point can be detected during acid-base titrations. They have different colours in acidic and alkaline solutions. Litmus is a common indicator. It is red in acidic solutions and blue in alkaline solutions.
Neutralization
When Arrhenius acid and Arrhenius base reacts, salt and water is formed as product, the reaction is known as neutralization reaction. For example:
Titration
Titration is a technique where a solution of known concentration is used to determine the concentration of an unknown solution. Typically, the titrant (the known solution) is added from a burette to a known quantity of the analyte (the unknown solution) until the reaction is complete.
Accuracy
The accuracy of analytical method is the closeness of obtained value to the true value of a sample. For example if we weight 2.5 mg of sample or substance but actual or known weight of sample is 10mg then this measurement is not accurate.
Acyclic Compounds or Aliphatic compounds or Open Chain Compounds
Open chain compounds contain carbon atoms linked in open chain. Open chain compounds are those in which the end carbon atoms are not joined with each other, in this way they form a long chain of carbon atoms. Open chain compounds are also called aliphatic compounds. e.g. n-pentane, isopentane etc.
Aldose Sugars
The carbohydrates which contain aldehydic group are called aldoses
Ketose Sugars
The carbohydrates which contain ketone group are referred as ketoses.
Alicyclic or Non-benzenoid Compounds
Carbocyclic compounds which do not have benzene ring in their molecules are called alicyclic or non-benzenoid compounds.
Analytical Chemistry
The analysis and separation of sample to detect and estimate its components through various techniques and instruments is known as analytical chemistry. It deals with instruments and methods to separate, identify and quantify the matter.
Aromatic Compounds/ Benzenoid Compounds
These organic compounds contain at least one benzene ring with six carbon atoms in their molecule. A benzene ring is made up of six carbon atoms with three alternating double bonds. They are called aromatic because of aroma or smell they have. e.g. benzene and naphthalene
The word Biochemistry (Bio = Life + Chemistry) means chemistry of life. This branch of chemistry deals with the study of with the naturally occurring macromolecules such as carbohydrates, proteins, lipids, nucleic acids and vitamins and various chemical and physical processes inside living system or organisms (plants and animals). It focuses on what is happening inside our cells and looks at how cells communicate with each other.
Enzymes
The word enzyme has a Greek origin which means that “in the yeast”. Enzymes are the class of proteins which are the complex polymeric nitrogenous organic biocatalysts produced by living cells that catalyze all types of biochemical reactions like digestion, respiration, muscular contraction and metabolism taking place in the living organisms. They are macromolecule that makes an unfavourable reaction able to occur. They accelerate the biochemical reactions and lead these reactions to completion which is not possible at ordinary temperature.
Peptide Linkage
The acid-amide (-CO-NH-) bond through which amino acids are linked in proteins by eliminating a water molecule is called Peptide Linkage. Due to this linkage protein is formed. When thousands of amino acids polymerize they form protein. A protein molecule formed with two amino acids is termed as dipeptide, with three tripeptide and so son. This linkage is formed by the removal of a water molecule b/w an -NH₂ group of an amino acid and -COOH group of another.
Fatty acids
Fatty acids are naturally occurring non-branched aliphatic monocarboxylic acids consisting of a long saturated or unsaturated lengthy hydrocarbon chain with a terminal carboxylic group mostly obtained from hydrolysis of natural fats and oils containing even number of carbon atoms (ranges C₁₂-C₂₀). They are long chain saturated or unsaturated carboxylic acids with a lengthy chain, either saturated or unsaturated. Fatty acids form esters (oils or fats) and glycerol in the presence of mineral acids. Fatty acids are building blocks of lipids. e.g. Palmitic acid; C₁₅H₃₁COOH, Stearic acid; C₁₇H₃₅COOH
Functional Group
An atom or group of atoms or multiple bonds which gives distinctive characteristic properties to an organic molecule is called functional group e.g. –OH group is the functional group of alcohol family (R–OH).
Isomerism
It is a phenomenon where two or more compounds have the same molecular formula but possesses different structural formulas and different properties. This is mainly because of different structural or spatial arrangements. Carbon compounds show phenomenon of isomerism by virtue of which a single molecular formula may represent two or more compounds.
Lipids
The lipids are a group of naturally occurring heterogeneous, water-insoluble, non-polar organic compounds of the plant and animal origins which includes fats, oils, waxes, and are insoluble in water but are easily soluble in Bloor’s reagent (a mixture of diethyl ether and ethyl alcohol in the ratio of 2:1) and organic solvents like ether, benzene, acetone, carbon tetrachloride and chloroform.
Catenation
The property of forming bonds with atoms of the same element is called catenation. It is the self-linking property of carbon.
Saccharides
Saccharides commonly known as Carbohydrates are naturally occurring organic compound are important food factor. Carbohydrates are macromolecules defined as polyhydroxy aldehydes or polyhydroxy ketones or large molecules that give these compounds on hydrolysis. They generally contain elements like carbon, hydrogen and oxygen.
Saponification
The chemical process for the preparation of soap is called saponification which is the reaction of triglycerides or fats or oils with sodium or potassium hydroxide to form glycerol and fatty acid salt called soap.
Lipids
Lipids are a group of naturally occurring heterogeneous organic compounds which includes fats, oils, waxes, and are insoluble in water but easily soluble in Bloor’s reagent (mixture of diethyl ether and ethyl alcohol in the ratio of 2:1) and organic solvents like ether, benzene, acetone, carbon tetrachloride and chloroform.
Bloor’s reagent
Bloor’s reagent is mixture of diethyl ether and ethyl alcohol in the ratio of 2:1 and it is used as a solvent for lipids.
Ozone hole
The ozone hole is a location where the ozone layer is depleted.
Organic chemistry
The study of covalent compounds of carbon and hydrogen (hydrocarbons) and their derivatives is called Organic Chemistry. All organic compounds contain carbon as an essential element. In short, it is chemistry of carbon containing compounds.
Environmental chemistry
Environmental Chemistry is the scientific study of the chemical and biological phenomena that occur in natural places. It is the field of chemistry deals with the study of reactions, origins, interactions, transport, effects along with the fates of all the chemical species present in the soil, water, and air environments, as well as the impact of human and biological activities on these.
Analytical Chemistry
The analysis and separation of sample to detect and estimate its components through various techniques and instruments is known as analytical chemistry. Analytical chemistry deals with instruments and methods to separate, identify and quantify the matter.
Qualitative Analysis
The identification of elements, ions or compounds present in a sample focusing only quality of substance is called Qualitative analysis.
Quantitative Analysis
The determination of exact amount of quantity of one or more substance present in compound or sample is called quantitative analysis. It deals with large number quantifying methods which are classified as physical or chemical methods.
Precision
The degree of agreement between replicate measurements of the same quantity is called precision. It is repeatability of a result and known as degree of exactness. Precision is measured how much detailed information is given and how much exactly measurement was taken.
Titrant
A titrant is a solution of known concentration that is added to another solution to determine the concentration of a second chemical species for example NaOH, HCl.
Anaylate
A chemical substance that is subject of chemical analysis or whose constituent are going to be measured is called analyte. For example 24 karat gold, NaCl, water etc.
Parameter
The parameter is measurable factor or boundary which define performance and quality of analytical methods. The validation a of analytical method is observed by parameters and various parameters of validation are selectivity, linearity, range, accuracy, precision and error.
2. Write down three differences between any one of the following:
(i) Saturated and unsaturated hydrocarbons
(ii) Fat and oil
(iii) Fat and water-soluble vitamins
(iv) Dextrorotary and Levorotatory Sugars
(v) Quantitative analysis and qualitative analysis
(vi) Reversible and irreversible reactions
(vii) Classical and Instrumental Methods
(viii) Troposphere and stratosphere
Answer
3. Define chemical equilibrium state. Why chemical equilibrium is dynamic? Explain it with one examples
Answer
Definition of Chemical Equilibrium
Chemical Equilibrium is the state of a reversible reaction (in a closed vessel) at which there is no observable change in the concentrations of reactants and products with time and rate of forward reaction is exactly equal to the rate of reverse reaction. Thus at equilibrium state:
Rate of forward reaction = Rate of backward reaction and Concentration remain constant
Chemical Equilibrium as Dynamic Equilibrium
The chemical equilibrium is dynamic in nature as both forward and reverse reactions are still occurring with same speed at all times even though the rates and concentrations are constant. Neither the forward reaction nor the reverse reaction has ceased to occur.
Example of attainment of equilibrium for hydrogen iodide formation form hydrogen and iodine
An example of reaction at equilibrium is a reaction of hydrogen and iodine vapours in a closed container to produce hydrogen iodide. At the start of reaction, there is a higher concentration of hydrogen and iodine and after that the concentration decreases as hydrogen iodide is formed. The concentration of hydrogen iodide increases as the forward reaction proceeds. As hydrogen iodide is formed, the reverse reaction is then able to occur. consequently the rate of the forward reaction will go on decreasing and the reverse reaction will go on increasing and ultimately the two rates will become equal to each other. Thus, the equilibrium will set up and concentration of various species (H₂, I₂, HI) becomes constant. It is represented as
Describe the characteristics of equilibrium constant. Why equilibrium constant may or may not have unit? Justify with example.
Answer
The equilibrium constant (Kc) of a reversible reaction is a constant ratio of Kf/Kᵣ (specific rate constant for forward reaction/specific rate constant for reverse reaction) at constant temperature. Equilibrium constant is a ratio of the product of the molar concentrations (active masses) of products to the product of molar concentrations (active masses) of reactants with each concentration term raised to the power of coefficient as expressed in the balanced chemical equation at constant temperature. Thus Kc is directly proportional to molar equilibrium concentrations (active masses) of products and inversely proportional to molar equilibrium concentrations (active masses) of reactants.
For a general reversible reaction; aA + bB ⇌ cC + dD, Kc is given by
The value of equilibrium constant does not depend on the initial concentrations of the reactants and the products. The value of Kc depends only on temperature i.e.
Importance of Kc
Kc determines which in greater concentration at equilibrium – the products or the reactants. In general:
(i) Kc > 1; equilibrium lies to the right and favours the product.
(ii) Kc < 1; equilibrium lies to the left and favours the reactants.
Unit of Kc
1. Kc has no units in reactions with equal number of moles on both sides of the equation. This is because concentration units cancel out in the expression for Kc.
e.g.
For the reaction; CO₂ (g) + H₂ (g) ⇌ CO₂ (g) + H₂O(l), Kc has no unit as the number of moles of reactants and products are equal in the balanced chemical equation. the unit of Kc is derived as
2. Kc has a unit for reactions when the number of moles of reactants and product are not equal,
e.g.
For the reaction; N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g); where the number of moles of reactants and products are not equal in the balanced chemical equation. the unit of Kc is derived as
6. State vital force theory and how was this theory discarded by Wohler?
Answer
Vital Force Theory
In 1885, Swedish chemist Jacob Berzelius put forward the “Vital Force Theory”. According to Vital Force Theory:
Organic compounds can only be formed in the tissues of living organisms (plants and animals) under the influence of a mysterious force called Vital Force, and cannot be synthesized form inorganic substances in the laboratory.
Demise (Rejection) of Vital Force Theory
In 1828, a German chemist Friedrich Wohler accidentally prepared the first organic compound Urea in the laboratory from an inorganic compound ammonium cyanate. Urea is a typical organic compound excreted in the urine of mammals.
Or
Write the names and structural formulae of six carbons alkanes, alkenes, alkyne, cycloalkane and aromatic hydrocarbons.
Answer
OR
Draw the structures of following compounds:
(i) 2,3-dimethylpentane
(ii) 3-ethyl-1-heptene
(iii) 1-butyne
(iv) 2,4-hexadiene
(v) 3-methyl-1,4-hexadiyne
(vi) 2-hepten-5-yn
(vii) 2-pentyne
(viii) neopentane
(ix) iso-propyl alcohol
(x) Phenol or toluene
(xi) iso-butane
(xii) Cyclohexane
Answer
7. Write down the molecular, structural and condensed formulae of the following compounds:
Answer
ORDefine functional group. Identify the functional groups in the following compounds and also write their names:
(a) CH₃CHO (Aldehydic group)
(c) CH₃COCH₃ (ketonic carbonyl group)
(d) C₃H₇COOH (carboxylic group)
(e) CH₂=CHCH₃
(f) CH₃COOCH₂CH₃ (ester group)
(g) CH₃CH₂Cl (chloride group)
(h) CH₃OCH₃
Answer
Functional Group
An atom or group of atoms or multiple bonds whose existence in an organic compound gives distinctive qualities to that compound is called a functional group.
Identification of Functional Group
8. Define salt and its three types with two examples each. Give three uses of salts. Also write any three methods of preparation of salts with equation.
Answer
Definition of Salt
A salt is an ionic crystalline compound which is the neutralization product (other than water) of an acid and base and it is the aggregation of cation (from base) other than H⁺ and anion (from acid) other than OH⁻. NaCl, CuCl₂ etc.
Three Types of Salts
1. Normal Salts (Salts obtained by complete neutralization of acid and base) e.g. NaCl, KNO₃, Na₂SO₄, K₃PO₄ etc.
2. Acidic Salts (Salts obtained by partial neutralization of an acid by a base) e.g. NaHCO₃, NaHSO₄, NH₄Cl etc.
3. Basic Salts (Salts obtained by partial neutralization of a base by an acid) e.g. Mg(OH)Cl, KCN, K₂CO₃ etc.
Three Uses of Salts
1. Chemical fertilizers used in agriculture by farmers are salts e.g. ammonium chloride, potassium chloride
2. Pesticides to kill or destroy insects, pests, weeds and fungi are salts e.g. copper(II) sulphate, iron(II) sulphate
4. Sodium hydrogen carbonate is used as a anti-acid to neutralize the excess acid secreted by the stomach.
5. Potassium permanganate(VII) is used as a disinfectant to kill bacteria.
6. In medical field, hydrated calcium sulphate (CaSO₄.2H₂O) is found in Plaster of Paris to make plaster casts for supporting broken bones.
7. Barium sulphate is used to make barium meals for patients who need to take an X-ray of their stomach. The salt helps to make internal organs like intestines appear on X-ray films.
Three Methods for the Preparation of Salts
Salts are prepared by the action of acids on metals, metal hydroxide (bases or alkalis), metal oxides, metal carbonates and metal bicarbonates. Salts are produced by the action of a base on a metal.
OR
Write one use of enzymes yeast, cellulose and amylase.
Answer
(i) yeast is used in the fermentation of molasses and starch to make alcohol (Ethanol).
(ii) cellulase is used in detergents to break down cellulose into water-soluble glucose
(iii) amylase is used as a sweetener in cuisine as well as in the baking of bread.
OR
What is homologous series? Name the any two common homologous series with examples. Write down the general characteristics of homologous series.
Answer
Definition of Homologous Series
Organic compounds are classified into classes based on the chemical properties. Each group or class is called homologous series which is a family or set of similar organic compounds having a same functional group which follows a regular structural pattern in which each successive members have a common difference of methylene (>CH₂) [or by molecular mass of 14]. Each member of series is called a Homologue of the other”. (in Greek, homo means same and logous means ratio).
Examples
General characteristics of homologous series
1. Identical structures and common difference in composition
Successive members of the series differ by one unit of -CH₂- and 14 units in their relative molecular mass. All members of a homologous series have identical structures.
2. General Molecular Formula
All members of a homologous series can be expressed by a general molecular formula.
For example
3. General Method of Preparation
All members of a homologous series can be prepared by a similar manner called general method of preparation
e.g. all members of alkanes can be prepared by reduction of alkyl halide by nascent hydrogen [H]:
4. Identical Chemical Properties
They have similar chemical properties because they contain the same functional group.
e.g. all alkanes are unreactive under ordinary conditions. They undergo combustion and substitution reaction with halogens.
OR
What is alkyl radicals? Give its type and general formula. Explain with structure different radicals of propane & butane.
Answer
Definition of Alkyl Radicals
The radicals obtained from alkanes by the removal of one hydrogen atom are called alkyl group or radical. They are generally represented by “R–” with general formula CₙH₂ₙ₊₁. Alkyl radicals are derivatives of alkanes.
Propyl Radical (It may exist in two isomeric forms)
Propane has a straight chain structure. When terminal H is removed, it is called n-propyl. When hydrogen from central carbon is removed, it is called isopropyl, as explained below:
Butyl Radical
Butyl radical is derived from butane (C₄H₁₀) having formula C₄
H₉–. It may exist in 4 isomeric forms.
H₉–. It may exist in 4 isomeric forms.
Butane has two isomers namely straight chain n-butane and branched chain iso-butane which gives total four isomeric alkyl groups, 2 are primary, 1 is secondary and 1 is tertiary.
n-butane has two types of carbon atoms i.e. primary and secondary so it gives two alkyl groups. Iso-Butane has primary and tertiary carbon so it gives two alkyl groups.
Details
When terminal H is removed from primary carbon of n-butane, it is called n-butyl/primary-butyl denoted as 1°.
When hydrogen from central or secondary carbon is removed from n-butane, it is called sec-butyl denoted as 2°.
When terminal H is removed from primary carbon of iso-butane, it is called iso-butyl.
When hydrogen from central or tertiary carbon is removed from iso-butane, it is called tert-butyl denoted as 3°.
9. Elaborate ionization equation of water. Explain in detail that how water ionization is related with pH of solution?
Answer
The water is a neutral liquid which has equal number of hydrogen (H⁺) and hydroxide (OH⁻) ion. Water is a weak electrolyte because it ionizes very slightly into ions in a process called auto-ionization or self-ionization which is characterized by an equilibrium constant (Kc) at a given temperature. Since a very small fraction of water molecules are ionized, the concentration of unionized water molecules is in large excess and is virtually constant. we can write the equilibrium (Kc) expression for auto-ionization for water as:.
H₂O ⇌ H⁺ + OH⁻ (auto-ionization equilibrium)
The equation constant (Kw) is called Ionic Product of water or Ionic-Product constant or Dissociation constant of water and it is equal to 1 x 10⁻¹⁴ (mol dm⁻³) ² or mol² dm⁻⁶. This constant determines absolutely the relative [H⁺] and [OH⁻] ions in water at this temperature. In pure water at 25°C, concentration of H⁺ and OH⁻ ions would always be equal and found to be 1 x 10⁻⁷ mol/dm³ (M). [That is why water is neutral at 25°C].
If the solution is acidic, then [H⁺] > [OH⁻] and if the solution is basic then [H⁺] < [OH⁻] but the ionic product Kw remains constant at 1 x 10⁻¹⁴ M² at 298K. For neutral solution [H⁺] = [OH⁻] =1 x 10⁻⁷ M. This [H⁺] is related with pH which is the negative log of [H⁺].
OR
Define buffers. What is the composition of buffers? Discuss its importance in our daily life.
Answer
Buffer
A buffer is an aqueous solution that has a highly stable pH and that can resist pH change upon the addition of acid or base. It is able to neutralize small amounts of added acid or base thus maintaining the pH of solution relatively stable. The pH of a buffer is independent of ionic strength. The pH of a buffer is dependent on temperature.
A buffering agent is a weak acid and its salt (conjugate base) with strong base or weak base and its salt (conjugate acid) with strong acid that helps to maintain the pH of an aqueous solution after adding another acid or base.
Two Types of Buffer or Composition of Buffer
1. Acidic buffer
They are made from weak acid and its salt with strong base (conjugate base)
e.g. CH₃COOH (weak acid)- CH₃COONa (salt or conjugate base)
2. Basic buffer
They are made from weak base and its salt with strong acid (conjugate acid)
e.g. NH₃ (weak base)-NH₄Cl (salt or conjugate acid)
Importance of Buffers
1. Maintenance of pH of Blood using combination of carbonate (H₂CO₃/NaHCO₃), phosphate (Na₂HPO₄ /NaH₂PO₄) and protein buffer systems.
2. Maintenance of pH in Laboratory Reactions
3. Maintenance of pH in various Industries like tanning of leather, manufacture of sugar, paper, drugs etc.
4. For Preparing Culture Media in Biological and Pathological Laboratories to maintain a constant pH for suitable growth of bacteria and viruses.
5. For Good Yield of Crops
6. For Preservation of foods and Fruits
7. Use in Other Sciences like molecular biology, microbiology, cell biology, soil sciences, nutrition & clinical analyses.
Answer
Three Uses of Carbohydrates
1. They are main energy providing materials or energy source for the survival of both plants and animals.
2. They sustain plant structure.
3. Carbohydrates, in the form of starch in plants and glucose in mammals, serve as energy storage.
Three Uses of Lipids
1. They act as transporter of fatty acids and fat soluble vitamins (A, D, E and K) in body.
2. They activate the enzymes.
3. Fats and oils are used for cooking and frying of food.
OR
What are amino acids and peptide bond? How peptide bond is formed? Also explain dipeptides & tripeptides.
Answer
Amino acids
Amino acids are building blocks of protein which are bi-functional organic compound containing an acidic carboxyl (–COOH) and a basic amino (–NH₂) groups and a distinct side chain ‘R’ which is different for different amino acids.
Peptide Bond or Linkage
A peptide linkage is an acid-amide bond formed between amino acids by the elimination of water. Due to this linkage protein is formed. When thousands of amino acids polymerize they form protein.
Formation of Peptide Bond
Dipeptides and tripeptides
A protein molecule formed with two amino acids is termed as dipeptide.
A protein molecule formed with three amino acids is termed as tripeptide.
11. Give reason:
Answer
(i) Why Silicon compounds are lesser than that of Carbon compounds?
Silicon compounds are less diverse than carbon compounds because silicon atoms are larger allowing lesser degree of catenation making it harder to form long chains and stable bonds. C–C bonds are much stronger (355 kJ mol⁻¹) than Si–Si (200 kJ mol⁻¹) bonds.
(ii) Why pure water is considered as weak electrolyte?
Pure water is considered as weak electrolyte because it gives very few ions on auto-ionization due to strong hydrogen bonding.
(iii) Justify the petroleum is ‘black gold’.
Petroleum is natural substance trapped in rocks beneath the Earth’s crust. The term petroleum refers to rock oil. Water, salts and earth particles are all present in this complex combination of gaseous, liquid and solid hydrocarbon. It is a liquid that is lighter than water yet insoluble in it.
Petroleum is referred to as 'black gold' because when black coloured crude oil extracted from the land is refined to give golden coloured distillate which worth like a gold due its oils and value. It is in less amount but economic value is extreme.
(iv) Alkanes are said to be saturated hydrocarbons.
Alkanes are said to be saturated hydrocarbons because they contain only C-C single bond with maximum number of hydrogen atoms having no scope of addition of any other atoms due to complete saturation of all the four valencies of carbon atom.
(v) Justify that water soluble vitamins are not injurious to health.
Water-soluble vitamins are rapidly excreted from the body. Hence, these vitamins are not toxic even if taken in large quantity. However, their deficiency causes disease.
(vi) Justify that greenhouse effect leads to global warming
Global warming refers to the gradual rise in Earth’s average surface temperature. The greenhouse effect or quantity of CO₂ in the air has a direct relationship with global warming effect. The greater the amount of CO₂, the greater the heat trapping or warming resulting in progressive rise in the surface’s average temperature leading to global warming.
(vii) Justify that “water is solvent”.
Water is a remarkable and excellent solvent and it is called Universal Solvent as it has the ability to dissolve practically all minerals. The high dissolving power of water is attributed due to its two distinct properties:
(i) Polar nature of water
(ii) Its extensive hydrogen bonding ability (Solvating tendency)
(viii) How is vegetable oil is converted into saturated fat (ghee)?
Vegetable oils are triester of glycerol and fatty acids of unsaturated long chains. Vegetable oil is converted into saturated fat ghee by the chemical process called hydrogenation. In this process unsaturated vegetable oil is treated with molecular hydrogen (H₂) in the presence of catalyst like nickel (ni) or palladium (Pd) at 250-300°C to form vegetable ghee (fat). This is an addition reaction of oil with H₂ to form an adduct called fat.
(ix) Why chemical equilibrium is considered dynamic not static?
Chemical equilibrium is considered dynamic because at equilibrium both forward and reverse reactions are taking place with same rate but in opposite directions. Since both reactions are not stopped, equilibrium is not static.
(x) Why the temperature on top of a mountain is colder than at sea level?
the temperature on top of a mountain is colder than at sea level due to low air density due to which its molecules are spread apart on account of decreased atmospheric pressure leading to fall in temperature.
12. Complete the following neutralization reactions between acids and bases.
Answer
OR
Define vitamin and complete the following chart
Answer
13. What are Oligosaccharides, Disaccharides and polysaccharides. Give their examples and sources.
OR
What are the carbohydrates? Explain sources and types of carbohydrates.
Answer
Definition of carbohydrates
Carbohydrates are naturally occurring organic compound are important food factor. Carbohydrates are macromolecules defined as polyhydroxy aldehydes or polyhydroxy ketones or large molecules that give these compounds on hydrolysis. They generally contain elements like carbon, hydrogen and oxygen.
General formula
They have general formula Cₙ(H₂O)ₙ showing that these compound contain hydrogen and oxygen in the ratio as in H₂O i.e. 2:1 (although they do not contain water molecules).
Classification of carbohydrates based on hydrolysis
Carbohydrates are classified as into three types based on hydrolysis:
Monosaccharides (Greek; Mono = one)
Definition
Monosaccharides are the simplest sugars which cannot be further simplified on hydrolysis.
No of Carbon atoms
They consist of 3 to 10 (9) carbon atoms.
Properties
Monosaccharides are white crystalline solids. They are soluble in water and have sweet taste. They cannot be hydrolyzed. They are reducing in nature, therefore, these are called reducing sugars.
Types
They are further classified according to the number of carbon atoms in their molecules as trioses, tetroses, pentoses, hexoses, and so on.
The important monosaccharides are hexoses like glucose and fructose, etc.
Glucose
1. Glucose (grape sugar) belongs to aldoses and fructose (honey) to ketones are examples of monosaccharides.
2. Glucose is obtained naturally as dextrorotatory and is present in grapes (20-30%), honey. It is also found in combined state in cane sugar, starch and cellulose.
3. Glucose is a rapid source of energy for patients. Fructose (Latin; fructus = fruit) occurs in ripe fruits, honey, cane sugar etc.
4. Glucose is a necessary component of human blood, that is why it is also known as blood sugar. The normal range for blood glucose is 65-110 mg (0.06-0.1%) per 100 mL.
5. Glucose is a pentahydroxy aldehyde (aldo hexose) while fructose is pentahydroxy ketone (keto hexose) having the open chain structures as follows and general formula C₆H₁₂O₆
Oligosaccharides (Greek; Oligo = few)
Definition
Oligosaccharides give 2 to 10 (9) units of monosaccharides on hydrolysis. In oligosaccharides, monosaccharides are linked with each other by glycosidic bond or linkage.
Properties
Oligosaccharides like monosaccharides are white, crystalline solids, sweet in taste and easily soluble in water. (They may be reducing or non-reducing).
Types
They are classified as disaccharides, trisaccharides, tetrasaccharides etc., depending upon the number of monosaccharides units they produce on hydrolysis.
Disaccharides
Disaccharides are those oligosaccharides which contain two monosaccharides. The most important oligosaccharides are disaccharides like sucrose. On hydrolysis, sucrose produces one unit of glucose and one unit of fructose.
Examples
Sucrose, maltose, lactose (milk sugar) are important members of disaccharides.
Polysaccharides
Definition
Polysaccharides are macromolecular carbohydrates also called polymeric carbohydrates giving more than 10 monosaccharides on hydrolysis consisting of hundreds to thousands of monosaccharides linked by glycosidic linkage.
Properties
Polysaccharides are amorphous, tasteless and insoluble in water. They are non-reducing in nature.
Examples of polysaccharides
1. Cellulose, starch (plant origin), glycogen (animal origin), amylose etc. are common polysaccharides. Cellulose is found in the cell walls, wood, linen, paper, cotton etc. Cotton contains 95% cellulose.
2. Starch occurs in cereals like wheat, rice, barley etc. and roots of potatoes.
3. Glycogen is also called animal starch found in muscles and liver of animals
Sources of Carbohydrates
14. What are amino acids and give their general structure? How many Essential and Non-essential Amino acids are there? Write down the range of Number of Amino acids and molecular weights of Proteins
Answer
Amino acids are building blocks of protein. They are bi-functional organic compound containing an acidic carboxyl (–COOH) and a basic amino (–NH₂) groups and a distinct side chain ‘R’ which is different for different amino acids.
Number of Amino acids in Proteins ----------- 60 to 6000 amino acids molecules.
molecule weight of proteins -------------------- 43000-50,000,000 daltons (1 dalton = 1amu).
Total Amino acids…………………………………….. 20
Essential Amino acids ……………………………… 10
Non-essential Amino acids………………………. 10
OR
What are fatty acids? Give their examples and chemical nature.
Answer
Definition of Fatty acids
Fatty acids are building blocks of lipids. They are long chain saturated or unsaturated carboxylic acids with a lengthy chain, either saturated or unsaturated. Fatty acids form esters (oils or fats) and glycerol in the presence of mineral acids.
Examples of Fatty acids
1. Palmitic acid; C₁₅H₁₃COOH
2. Stearic acid; C₁₇H₅₃COOH
Chemical Nature
Lipids are macromolecules made up of fatty acids. Lipids include oils and fats. Oils and fats are triesters of long chain carboxylic (fatty) acids with glycerol. These esters are made of three fatty acids, therefore, they are called triglycerides or triesters. General formula of triglycerides is as under.
15. Briefly describe any three beneficial impacts of pharmaceutical industry on human society.
Answer
Importance of Pharmaceutical Industry
Pakistan’s pharmaceutical business has risen significantly in recent decades. Pharmaceutical forms are always working on novel therapies that will help people live longer, healthier lives. Here are some of the industry’s most important contributions, as well as why pharmaceutical firms are so vital to patients, society, and the life sciences industry.
1. Treatments increase life expectancy
The pharmaceutical business has made a significant contribution to the global increase in life expectancy for men and women. Pharmaceutical improvements are said to have responsible for 73% of the entire increase in life expectancy between 2000 and 2009 in 30 developing and high-income nations.
2. The industry strives to eradicate and eliminate diseases
When it comes to creating remedies, the ultimate objective is disease elimination, as this helps ecosystems on a worldwide scale. Smallpox is the first and so far only – human illness to be declared eliminated globally, according to the World Health Organization (WHO).
3. Reduced pain and suffering
According to a research conducted by the World Health Organization, people who live with chronic pain are four times more likely to have melancholy, anxiety, and difficulties working than those who do not.
16. Write down causes of following diseases:
(i) Diarrheal Diseases
(ii) Dysentery
(iii) Cholera
(iv) Crytosporidium
(v) Fluorosis
(vi) Hepatitis
(vii) Hookworm
(viii) Typhoid
Answer
17. What is the cause of acid rain? Explain. Write down the effects of acid rain and global warming.
Answer
Definition
Acid rain means the presence of excessive acids in rainwater, which are formed when the number of gaseous air pollutants like nitrogen dioxide and sulphur dioxide in the environment reacts with rainwater resulting in the formation sulphuric acid and nitric acid, which causes its decreasing pH value. When the concentration of rain has a pH value less than 5.5 is said to be acid rain. Acid rain is one of the consequences of air pollution.
Reason of formation of Acid Rain
1. The burning of fossil fuels produces oxides of sulphur and nitrogen (SO₂, NO, NO₂) into the atmosphere.
2. Rainwater converts SO₂ into H₂SO₄ and oxides of nitrogen i.e. NO and NO₂ into HNO₂ and HNO₃ respectively.
3. Rainwater is weakly acidic due to dissolved CO₂ of the air having a pH of 5.6 to 6.
4. Rainwater becomes more acidic and its pH reduced to 4 on dissolving air pollutants (i.e. acids).
5. Acid rain is formed on dissolving acidic air pollutant like sulphur dioxide and nitrogen oxides forming acids by rainwater.
Harmful Effects of Acid Rain
Acid rain causing harm to soil, animals, plants and aquatic life.
(i) Effects on Buildings and Monuments
Acid rain attacks and eats away the calcium carbonate present in the marble and limestone of many buildings and monuments. Consequently, these structures are getting increasingly dull and degraded day by day.
(ii) Effects on Aquatic Life
Acid rain on soil and rocks leaches heavy metals (AI, Hg, Pb, Cr, etc.) and discharges them into rivers and lakes. Humans consumes this water as a source of drinking water. These metals accumulate in human body to a toxic level.
On the other hand, the aquatic life in lakes, suffers because of the high concentration of these metals. Especially, the high concentration of aluminum ions clogs the fish gills. It causes suffocation and ultimately death of fish.
3. Effects on Trees and Plants
Acid rain directly damages the trees and plant leaves, limiting their growth. Plants development may hampered depending on the severity of the damage. Plants’ capacity to withstand cold or illnesses deteriorates, and they eventually perish.
4. Effect on Soil
Acid rain increases the acidity of the soil. Many crops and plants cannot grow properly in such acidic soil. It also increases the levels of toxic metals in the soil, which damage the plants. the acidity of the soil, even affects old trees. Their growth is retarded becoming dry and die.
OR
What are primary and secondary air pollutants? Or Give difference between primary and secondary air pollutants. Identify as primary or secondary air pollutant SO₂, CH₄, HNO₃, NH₃, H₂SO4 and O₃
Answer
Primary Pollutants Vs Secondary Pollutants
Primary pollutants are the waste or exhaust products driven out because of the combustion of fossil fuels and organic materials. These are the oxides of sulphur (CO₂, SO₃), oxides of carbon (CO, CO₂), oxides of Nitrogen (especially nitric oxide NO and nitrogen dioxide, NO₂), hydrocarbons or greenhouse gases like CH₄, ammonia (NH₃) and fluorine compounds (CFCs)
Secondary pollutants are produced from various reaction of Primary pollutants together through a variety of processes. They include Sulphuric acid, nitric acid, carbonic acid, hydrofluoric acid, ozone and peroxy acetyl nitrate (PAN, CH₃–CO–O–O–NO₂).
18. Describe the composition of water. Write degree of Hardness of water on the basis of Dissolved Ca Ions (mg/L)
Answer
Rain water is considered as purest form of water. Drinking water contains ions like Na⁺, K⁺, Mg²⁺, Cl⁻ etc. necessary for our body.
Structure of Water
Water is simple covalent molecule comprising of one O atom bonded to two H atoms through single covalent bonds. Water is a polar molecule due to difference in electronegativity between H and O.
Due to higher electronegativity of the oxygen atom, the O–H bonds of water is highly polar in nature. The oxygen atoms attracts the shared electron pair of the covalent bonds towards itself to a greater extent than the H atoms acquiring a partial negative charge (δ−) while the both H atoms acquire a partial positive charge (δ+) thereby making the bond polar forming a dipole.
Degree of Hardness of water on the Basis of Dissolved Ca Ions (mg/L)
Soft water ………………….. 0 to 16.1 mg/L
Slightly hard water ……….. 16.1 to 60 mg/L
Moderate hard water ……. 61 to 120 mg/L
Hard water ………………. 121 to 180 mg/L
Very hard water …………. More than 180 mg/L
19. List down the applications of conductometry?
Answer
Applications
1. Degree of dissociation constant can be determined.
2. Solubility of a sparingly soluble can be determined.
3. Rate constant of a reaction can be studied.
4. End point of titration can be determined.
20. What is error? Write down causes of errors with their %. Write down brief note systematic and random errors with two examples each.
OR
Describe fractional distillation of petroleum with its 5 fractions.
Answer
Petroleum is a naturally occurring dark brownish or greenish black coloured thick viscous liquid with bad smell found in underground deposits in various parts of earth at different depths comprising of a complex mixture of gaseous, liquid and solid hydrocarbons (ranging C1 to C40) like alkanes, alkenes, cycloalkanes, aromatic hydrocarbons together with the varying but small quantities of inorganic compounds of nitrogen, oxygen, and sulphur and earthy particles.
Separation of Petroleum Fractions by fractional distillation
The various components of petroleum is separated into fractions by fractional distillation (separation of fractions or components depending upon their boiling point ranges). More than 500 compounds have been formed in petroleum distillate boiling below 200°C. Each fraction is not a single compound, rather each of it consists of different organic compounds.
21. A solution of HCl has pH of 2.3. Calculate its pOH and [H+]?
OR Find pH, pOH, [OH−] and [H+] of 2.46 × 10−9 M KOH solution.
🚨 ⚡ Class 10 Exam 2026 Key MCQs: Master These Key MCQs for a Perfect Score! 🧑🏫💯" 🚀 Boost Your Score! 🎯
🎨 💥 Textbook MCQs on Chemical Equilibrium – Must Know Questions for Exams!
1. Which one of the following statements is FALSE about dynamic equilibrium?
🟩 A. Concentration of reactant and products are not changed
🟪 B. It takes place in a closed container
🟨 C. Rate of forward reaction equals rate of reverse reaction
🟦 D. Equilibrium cannot be disturbed by any external stress✔️
2. When the magnitude of Kc is small, it indicates:
🟩 A. Reaction mixture contains most of the reactant✔️
🟪 B. Reaction mixture contains most of the product
🟨 C. Nearly equal amounts of reactant and product
🟦 D. Reaction goes to completion
3. Qc can be defined as:
🟩 A. Ratio of product and reactant
🟪 B. Ratio of molar concentration of product and reactant at specific time✔️
🟨 C. Ratio of concentration of product and molar volume of reactant
🟦 D. Ratio of concentrations raised to coefficients
4. For the reaction
4NH₃(g) + 5O₂(g) ⇌ 4NO(g) + 6H₂O(g)
Which expression represents Kc?
🟩 A. [NO]⁴ [H₂O]⁶ / [NH₃]⁴ [O₂]⁵✔️
🟪 B. [NH₃]⁴ [O₂]⁵ / [NO]⁴ [H₂O]⁶
🟨 C. [NO][H₂O]/[NH₃][O₂]
🟦 D. [Products]/[Reactants] without exponents
5. For which system does Kc have units of concentration?
🟩 A. N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ✔️
🟪 B. N₂(g) + O₂(g) ⇌ 2NO(g)
🟨 C. H₂(g) + I₂(g) ⇌ 2HI(g)
🟦 D. CO₂(g) + H₂(g) ⇌ CO(g) + H₂O(g)
6. A reaction that does not go to completion is reversible. It is represented by:
🟩 A. Double straight line
🟪 B. Single arrow
🟨 C. Double arrow✔️(⇌ style representation)
🟦 D. Dotted lines
7. The unit of Kc for the reaction
N₂(g) + O₂(g) ⇌ 2NO(g)
🟩 A. mol dm⁻³
🟪 B. mol⁻² dm⁶✔️
🟨 C. mol⁻¹ dm³
🟦 D. No unit
8. The system is stable in equilibrium when:
🟩 A. Qc = Kc✔️
🟪 B. Qc > Kc
🟨 C. Qc < Kc
🟦 D. None
9. The value of Kc increases when:
🟩 A. [Reactant] = [Product]
🟪 B. Product concentration is more✔️
🟨 C. More reactant is present
🟦 D. Less product is present
10. Which of the following represent backward reaction?
🟩 A. (i) and (ii)
🟪 B. (ii) only✔️
🟨 C. (i) only
🟦 D. (iii) only
✅ Answer Key with Short Reasons
1️⃣ D — External stress (temperature, pressure, concentration) can disturb equilibrium.
2️⃣ A — Small Kc means reactants are favoured.
3️⃣B — Qc is ratio of concentrations at any moment, not equilibrium.
4️⃣A — Kc = products⁴⁺⁶ / reactants⁴⁺⁵ using coefficients as powers.
5️⃣A — Δn ≠ 0 gives units; here Δn = 2 − 4 = −2.
6️⃣ C — Reversible reactions use double arrows (⇌ / dotted).
7️⃣ B — Units depend on Δn (change in moles of gas).
8️⃣ A — A system is at equilibrium when Qc equals Kc.
9️⃣ B — Higher product concentration → larger Kc value.
🔟 B — Statement (ii) alone shows backward reaction.
🎨 💥 Textbook MCQs on Acids, Bases & Salts – Must Know Questions for Exams!
1. Corrosive effect on skin is caused by:
🟩 A. Acid
🟪 B. Base
🟨 C. Salt
🟦 D. Both a and b✔️
2. Preservatives are used to preserve:
🟩 A. Acid
🟪 B. Base
🟨 C. Food✔️
🟦 D. Water
3. Which of the following is NOT an Arrhenius acid?
🟩 A. HCl
🟪 B. CO₂✔️
🟨 C. HNO₃
🟦 D. H₂SO₄
4. NH₃ can be a base according to:
🟩 A. Arrhenius theory
🟪 B. Bronsted–Lowry theory
🟨 C. Lewis theory
🟦 D. Both b and c✔️
5. Which of the following is a Lewis base?
🟩 A. HNO₃
🟪 B. CN⁻✔️
🟨 C. HCl
🟦 D. AlCl₃
6. A substance that donates a pair of electrons to form a coordinate covalent bond:
🟩 A. Bronsted–Lowry base
🟪 B. Bronsted–Lowry acid
🟨 C. Lewis acid
🟦 D. Lewis base✔️
7. If pH value is greater than 7, the solution is:
🟩 A. Acidic
🟪 B. Basic✔️
🟨 C. Amphoteric
🟦 D. Neutral
8. Salt among the following is:
🟩 A. HCl
🟪 B. KCl✔️
🟨 C. HNO₃
🟦 D. H₂SO₄
9. Substances that react with both acids and bases are called:
🟩 A. Amphoteric substances✔️
🟪 B. Conjugate acids
🟨 C. Conjugate bases
🟦 D. Buffers
10. The reaction of an acid and a base to form salt and water is called:
🟩 A. Hydration
🟪 B. Neutralization✔️
🟨 C. Hydrolysis
🟦 D. Both a and c
✅ Answer Key with Short Reasons
1️⃣ D — Both acids and bases can cause burns.
2️⃣C — Preservatives prevent spoilage of food.
3️⃣B — CO₂ does not produce H⁺ ions directly in water (not Arrhenius acid).
4️⃣D — NH₃ accepts a proton (Bronsted) and donates lone pair (Lewis).
5️⃣B — CN⁻ has lone pairs available → Lewis base.
6️⃣D — Lewis base donates an electron pair.
7️⃣B — pH > 7 means basic.
8️⃣B — KCl is a salt formed from KOH + HCl.
9️⃣ A — Amphoteric substances react with both acids and bases.
🔟B — Neutralization = acid + base → salt + water.
🎨 💥 Top Textbook MCQs on Organic Chemistry You Can’t Miss!
1. The branch of chemistry that deals with hydrocarbons and their derivatives is:
🟩 A. Organic chemistry✔️
🟪 B. Inorganic chemistry
🟨 C. Physical chemistry
🟦 D. Biochemistry
2. The general formula of alkanes is:
🟩 A. CₙH₂ₙ
🟪 B. CₙH₂ₙ₊₁
🟨 C. CₙH₂ₙ₊₂✔️
🟦 D. CₙH₂ₙ₋₂
3. Which of the following is an alcohol?
🟩 A. CH₃CHO
🟪 B. CH₃CH₂OCH₃
🟨 C. CH₃OH✔️
🟦 D. HCOOH
4. Which of the following is a saturated hydrocarbon?
🟩 A. CH₃CH=CH₂
🟪 B. CH₃CH₂CH₃ ✔️
🟨 C. CH₃C≡CH
🟦 D. CH₂=CH–C≡CH
5. The prefix “hept–” stands for how many carbon atoms?
🟩 A. 2
🟪 B. 5
🟨 C. 7✔️
🟦 D. 9
6. The functional group –COOH is characteristic of:
🟩 A. Alkynes
🟪 B. Carboxylic acids✔️
🟨 C. Phenols
🟦 D. Alcohols
7. Polyethene is:
🟩 A. Oil
🟪 B. Paper
🟨 C. Plastic✔️
🟦 D. Wood
8. Acetic acid is obtained from:
🟩 A. Banana
🟪 B. Dates
🟨 C. Garlic
🟦 D. Vinegar✔️
9. CH₃–CH₂– is a/an ______ radical.
🟩 A. Methyl
🟪 B. Ethyl✔️
🟨 C. n-propyl
🟦 D. iso-propyl
10. Alkenes:
🟩 A. Show same general formula as alkynes
🟪 B. Have carbon–carbon triple bond
🟨 C. Have carbon–carbon double bond✔️
🟦 D. Are saturated hydrocarbons
✅ Answer Key with Short Reasons
1️⃣A — Organic chemistry studies hydrocarbons and their derivatives.
2️⃣C — Alkanes follow the formula CₙH₂ₙ₊₂ (single bonds).
3️⃣C — CH₃OH contains –OH group → alcohol.
4️⃣B — Saturated hydrocarbons have only single bonds (alkanes).
5️⃣C — “Hept–” = 7 carbons (IUPAC prefix).
6️⃣B — –COOH is the functional group of carboxylic acids.
7️⃣C — Polyethene is a commonly used plastic.
8️⃣D — Vinegar contains acetic acid.
9️⃣B — CH₃–CH₂– is the ethyl radical.
🔟C — Alkenes contain a C=C double bond.
🎨 💥 Textbook-Based Biochemistry MCQs Every Student Must Know
1. Glucose is:
🟩 A. Vitamin
🟪 B. Protein
🟨 C. Carbohydrate✔️
🟦 D. Lipid
2. The deficiency of vitamin D causes:
🟩 A. Beriberi
🟪 B. Rickets✔️
🟨 C. Scurvy
🟦 D. Haemorrhage
3. ______ encodes genetic information.
🟩 A. RNA
🟪 B. DNA✔️
🟨 C. Progesterone
🟦 D. Cholesterol
4. Carbohydrates containing an aldehyde group are called:
🟩 A. Saccharides
🟪 B. Ketoses
🟨 C. Pentose
🟦 D. Aldoses✔️
5. Amino acids are the building blocks of:
🟩 A. Nucleic acids
🟪 B. Proteins✔️
🟨 C. Vitamins
🟦 D. Lipids
6. Which one of the following is a polysaccharide?
🟩 A. Fructose
🟪 B. Maltose
🟨 C. Starch✔️
🟦 D. None
7. Lactose is:
🟩 A. Grape sugar
🟪 B. Honey sugar
🟨 C. Milk sugar✔️
🟦 D. Cane sugar
8. Cotton contains ___ cellulose.
🟩 A. 30%
🟪 B. 65%
🟨 C. 85%
🟦 D. 95%✔️
9. What is true about a peptide?
🟩 A. It is a protein
🟪 B. It is an anhydride of carboxylic acids
🟨 C. It is an anhydride of an amine
🟦 D. It is a polyamide✔️
10. Fats are solids at:
🟩 A. Ordinary room temperature✔️
🟪 B. High temperature
🟨 C. Above 50°C
🟦 D. None of them
✅ Answer Key with Short Reasons
1️⃣C — Glucose is a simple carbohydrate (monosaccharide).
2️⃣B — Vitamin D deficiency leads to weak bones → rickets.
3️⃣B — DNA stores and carries genetic information.
4️⃣D — Aldoses are sugars containing an aldehyde group.
5️⃣B — Proteins are polymers of amino acids.
6️⃣C — Starch is a polysaccharide (many glucose units).
7️⃣C — Lactose is milk sugar (glucose + galactose).
8️⃣D — Cotton is made of ~95% cellulose.
9️⃣D — Peptides are chains of amino acids linked by amide (peptide) bonds.
🔟A — Fats remain solid at ordinary room temperature.
🎨 💥 Textbook-Based Environmental Chemistry (The Atmosphere) MCQs Every Student Must Know 🌍✨
1. Second highest layer of Earth’s atmosphere is:
🟩 A. Stratosphere
🟪 B. Mesosphere✔️
🟨 C. Troposphere
🟦 D. Thermosphere
2. Aeroplanes fly in:
🟩 A. Troposphere✔️
🟪 B. Stratosphere
🟨 C. Mesosphere
🟦 D. Thermosphere
3. The altitude of the stratosphere is:
🟩 A. 40–45 km
🟪 B. 50–55 km✔️
🟨 C. 60–65 km
🟦 D. 70–75 km
4. The layer that separates the stratosphere and troposphere is:
🟩 A. Tropopause✔️
🟪 B. Mesopause
🟨 C. Thermopause
🟦 D. Stratopause
5. Ozone layer is part of:
🟩 A. Mesosphere
🟪 B. Stratosphere✔️
🟨 C. Thermosphere
🟦 D. Troposphere
6. Which is NOT a greenhouse gas?
🟩 A. Carbon dioxide
🟪 B. Methane
🟨 C. Nitrous oxide
🟦 D. Oxygen✔️
7. Second most abundant constituent of dry air after nitrogen is:
🟩 A. Nitrogen
🟪 B. Oxygen✔️
🟨 C. Carbon dioxide
🟦 D. Helium
8. Ozone is mainly found in the ______ layer:
🟩 A. Troposphere
🟪 B. Mesosphere
🟨 C. Stratosphere✔️
🟦 D. Exosphere
9. Which of the following is a reason for global warming?
🟩 A. Presence of sulphite
🟪 B. Rise in CO₂ concentration✔️
🟨 C. Oxides of nitrogen
🟦 D. Formation of ozone
10. Atmospheric pressure decreases with:
🟩 A. Increase in longitude
🟪 B. Decrease in altitude
🟨 C. Increase in altitude✔️
🟦 D. Increase in latitude
✅ Answer Key with Short Reasons
1️⃣B — Mesosphere lies above the stratosphere; it is the second highest layer.
2️⃣A — Aircraft fly mainly in the troposphere.
3️⃣B — Stratosphere extends roughly between 50–55 km.
4️⃣A — Tropopause separates troposphere and stratosphere.
5️⃣B — The ozone layer lies in lower stratosphere.
6️⃣D — Oxygen is not a greenhouse gas.
7️⃣B — Oxygen makes up ~21% of dry air after nitrogen.
8️⃣C — Most ozone is concentrated in the stratosphere.
9️⃣B — Higher CO₂ concentration enhances the greenhouse effect.
🔟C — Air pressure decreases as altitude increases.
🎨 💥 Textbook-Based Environmental Chemistry Part II (Water)MCQs Every Student Must Know 🌍💧
1. Which of the following water-borne diseases is of viral origin?
🟩 A. Typhoid fever
🟪 B. Polio✔️
🟨 C. Dysentery
🟦 D. Diarrhea
2. How much percentage of the Earth’s surface is covered with water?
🟩 A. 70%✔️
🟪 B. 60%
🟨 C. 90%
🟦 D. 75%
3. Which type of bond is formed between H₂O molecules?
🟩 A. Hydrogen bond✔️
🟪 B. Ionic bond
🟨 C. Covalent bond
🟦 D. All of these
4. Permanent hardness of water is due to the presence of:
🟩 A. MgSO₄✔️
🟪 B. Mg(HCO₃)₂
🟨 C. Ca(HCO₃)₂
🟦 D. All of these
5. How much fresh water is present in rivers and lakes?
🟩 A. 0.3%
🟪 B. 3%✔️
🟨 C. 0.2%
🟦 D. 2%
6. The taste of pure water is:
🟩 A. Sour
🟪 B. Bitter
🟨 C. Sweet
🟦 D. Tasteless✔️
7. Which of the following is helpful in removing permanent hardness?
🟩 A. Na₂CO₃✔️
🟪 B. Ca(OH)₂
🟨 C. CaCO₃
🟦 D. Na₂SO₄
8. Which salts are dissolved in water to make temporary hard water?
🟩 A. CaSO₄ and CaCl₂
🟪 B. KNO₃ and KOH
🟨 C. CaCO₃ and Ca(OH)₂
🟦 D. Ca(HCO₃)₂ and Mg(HCO₃)₂✔️
9. Water is a:
🟩 A. Polar solvent✔️
🟪 B. Non-polar solvent
🟨 C. Amphipathic solvent
🟦 D. Non-polar charged solvent
✅ Answer Key with Short Reasons
1️⃣B — Polio virus spreads through contaminated water.
2️⃣A — About 70% of Earth’s surface is covered with water.
3️⃣A — Hydrogen bonds form between water molecules.
4️⃣A — Permanent hardness is caused by sulphates (MgSO₄, CaSO₄).
5️⃣B — Freshwater in rivers and lakes is about 3%.
6️⃣D — Pure water is tasteless.
7️⃣A — Sodium carbonate removes permanent hardness by precipitation.
8️⃣D — Temporary hardness is due to bicarbonates of Ca and Mg.
9️⃣A — Water has polar O–H bonds → overall polar molecule.
🎨 💥 Textbook-Based Analytical Chemistry (Chapter 7)MCQs Every Student Must Know 🔬📊
1. Analytical chemistry deals with instruments and methods to ______, identify and quantify matter.
🟩 A. Mix
🟪 B. Separate✔️
🟨 C. Differentiate
🟦 D. Manipulate
2. The sample may be solid, liquid, gas or a ______ in qualitative analysis.
🟩 A. Mixture✔️
🟪 B. Compound
🟨 C. Substance
🟦 D. None
3. Analysis dealing with identification of functional groups in compounds is:
🟩 A. Physical qualitative analysis
🟪 B. Analytical qualitative analysis
🟨 C. Organic qualitative analysis✔️
🟦 D. Inorganic qualitative analysis
4. Flame test of copper halide shows bluish-green colour indicating presence of:
🟩 A. Halogen
🟪 B. Hydrogen
🟨 C. Copper✔️
🟦 D. b and c
5. The physical methods used to measure physical properties are called:
🟩 A. Combustion analysis method
🟪 B. Atomic emission spectroscopy method✔️
🟨 C. Volumetric analysis method
🟦 D. Gravimetric analysis method
6. The error caused by improper functioning of an instrument is:
🟩 A. Determinant error
🟪 B. Indeterminant error
🟨 C. Systematic error
🟦 D. Both a & c✔️
7. Agreement between measured value and true accepted value is:
🟩 A. Error
🟪 B. Accuracy✔️
🟨 C. Precision
🟦 D. All of these
8. Spectroscopy is the interaction of light with:
🟩 A. Liquid
🟪 B. Solid
🟨 C. Gas
🟦 D. Matter✔️
9. Gas is the mobile phase in:
🟩 A. Liquid chromatography
🟪 B. Solid chromatography
🟨 C. Gas chromatography✔️
🟦 D. None of these
10. Used to assess concentration or amount of an atomic/molecular/ionic substance:
🟩 A. Chromatography
🟪 B. Spectroscopy✔️
🟨 C. Conductometry
🟦 D. Potentiometry
✅ Answer Key with Short Reasons
1️⃣B — Analytical chemistry separates, identifies, quantifies matter.
2️⃣A — Samples can be mixtures in qualitative analysis.
3️⃣C — Functional group detection belongs to organic qualitative analysis.
4️⃣C — Copper salts show a characteristic bluish-green flame.
5️⃣B — Atomic emission spectroscopy measures physical properties of atoms.
6️⃣D — Instrument malfunction causes systematic/determinate errors.
7️⃣B — Accuracy = closeness to true value.
8️⃣D — Spectroscopy studies how light interacts with all forms of matter.
9️⃣C — Gas chromatography uses gas as mobile phase.
🔟B — Spectroscopy determines concentration using light–matter interaction.
🎨 💥 Textbook-Based Chemical Industries (Chapter 8)MCQs Every Student Must Know 🏭🧪
1. Soap is the term for salts of a:
🟩 A. Carboxylic group
🟪 B. Citric acid
🟨 C. Sulphuric acid
🟦 D. Fatty acid✔️
2. Surfactants reduce the ______ of water.
🟩 A. Viscosity
🟪 B. Surface tension✔️
🟨 C. Boiling point
🟦 D. Melting point
3. The carboxylate end of a soap molecule attracted to water is called:
🟩 A. Hydrophobic end
🟪 B. End point
🟨 C. Hydrophilic end✔️
🟦 D. None of them
4. The use of potassium hydroxide produces a:
🟩 A. Hard soap
🟪 B. Soft soap✔️
🟨 C. Moderate soap
🟦 D. All of these
5. Citric acid is used in cold drinks for:
🟩 A. Sweet taste
🟪 B. Bitter taste
🟨 C. Sour taste✔️
🟦 D. Salty taste
6. The centrifuge machine is used for separation of:
🟩 A. Juice
🟪 B. pH
🟨 C. Mud
🟦 D. Crystal✔️
7. Abrasives are:
🟩 A. Water-soluble minerals
🟪 B. Water-insoluble minerals✔️
🟨 C. Water semi-soluble minerals
🟦 D. Water-absorbing minerals
8. Harvesting is the most important step of:
🟩 A. Preparation of soap
🟪 B. Preparation of cold drinks
🟨 C. Preparation of sugar✔️
🟦 D. Preparation of medicines
9. Which of the following is used as jet fuel?
🟩 A. Kerosene oil✔️
🟪 B. Diesel oil
🟨 C. Fuel oil
🟦 D. Petrol
10. Which one of the following is NOT a fraction of crude oil?
🟩 A. Paraffin wax
🟪 B. Ammonia
🟨 C. Fuel oil
🟦 D. Petroleum coke✔️
✅ Answer Key with Short Reasons
1️⃣ D Soaps are sodium/potassium salts of fatty acids.
2️⃣ B Surfactants reduce surface tension, helping cleaning.
3️⃣ C The polar ionic end is hydrophilic (water-loving).
4️⃣ B KOH makes soft soap, NaOH makes hard soap.
5️⃣ C Citric acid provides sour taste in drinks.
6️⃣ D Centrifuge separates crystals by spinning.
7️⃣ B Abrasives are hard, insoluble minerals (e.g., silica).
8️⃣ C Sugar industry requires harvesting sugarcane.
9️⃣A Jet fuel is based on kerosene.
🔟 D Petroleum coke is a residual solid, not a crude fraction.
📝🔥 Unlock Success: Most Important Class 10 MCQs for the 2026 Exam! 🚀💡
1. Consider the reaction:
4NO(g) + 6H₂O(g) ⇌ 4NH₃(g) + 5O₂(g)
Expression for equilibrium constant Kc:
🟩 A. [NH₃]⁴ [O₂]⁵ / [NO]⁴ [H₂O]⁶ ✔️
🟪 B. [NO]⁴ [H₂O]⁶ / [NH₃]⁴ [O₂]⁵
🟨 C. [NH₃][O₂] / [NO][H₂O]
🟦 D. [NO][H₂O] / [NH₃][O₂]
2. For which system does Kc have units of concentration?
🟩 A. ✔️ N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
🟪 B. N₂(g) + O₂(g) ⇌ 2NO(g)
🟨 C. H₂(g) + I₂(g) ⇌ 2HI(g)
🟦 D. CO₂(g) + H₂(g) ⇌ CO(g) + H₂O(g)
3. Which of the following is NOT an Arrhenius acid?
🟩 A. HCl
🟪 B. ✔️ SO₂
🟨 C. HNO₃
🟦 D. H₂SO₄
4. Substances that react with both acids and bases are called:
🟩 A. ✔️ Amphoteric substances
🟪 B. Conjugate acids
🟨 C. Conjugate base
🟦 D. Buffers
5. Which of the following is a saturated hydrocarbon?
🟩 A. CH₃CH=CH₂
🟪 B. ✔️ CH₃CH₂CH₂CH₃
🟨 C. CH₃C≡CH
🟦 D. CH₂=CH–C≡CH
6. CH₃–CH₂–CH₂– is … radical:
🟩 A. Methyl
🟪 B. Ethyl
🟨 C. ✔️ n-Propyl
🟦 D. iso-Propyl
7. Surfactants reduce the ______ of water.
🟩 A. Viscosity
🟪 B. ✔️ Surface tension
🟨 C. Boiling point
🟦 D. Melting point
8. The carboxylate end of a soap molecule attracted to water is called:
🟩 A. Hydrophobic end
🟪 B. End point
🟨 C. ✔️ Hydrophilic end
🟦 D. None of them
9. Lactose is:
🟩 A. Grape sugar
🟪 B. Honey sugar
🟨 C. ✔️ Milk sugar
🟦 D. Cane sugar
10. The altitude of stratosphere is:
🟩 A. 40 to 45 km
🟪 B. ✔️ 50 to 55 km
🟨 C. 60 to 65 km
🟦 D. 70 to 75 km
11. Layer of atmosphere which separates stratosphere and troposphere is known as:
🟩 A. ✔️ Tropopause
🟪 B. Mesopause
🟨 C. Thermopause
🟦 D. Stratopause
12. Which is NOT part of greenhouse gases?
🟩 A. Carbon dioxide
🟪 B. Methane
🟨 C. Nitrous oxide (N₂O)
🟦 D. ✔️ Oxygen (O₂)
13. It is used for surfacing roads:
🟩 A. Naphtha
🟪 B. Paraffin
🟨 C. Coal
🟦 D. ✔️ Bitumen
14. The general formula of an alkyl radical is:
🟩 A. CₙH₂ₙ₊₂
🟪 B. CₙH₂ₙ₋₂
🟨 C. ✔️ CₙH₂ₙ₊₁
🟦 D. CₙH₂ₙ
15. Infrared radiation generated by Earth’s surface is absorbed in air by higher concentration of:
🟩 A. CH₄
🟪 B. O₃
🟨 C. ✔️ CO₂
🟦 D. N₂O
16. The permanent hardness of water is due to presence of:
🟩 A. ✔️ MgSO₄
🟪 B. Mg(HCO₃)₂
🟨 C. Ca(HCO₃)₂
🟦 D. All of these
17. Flame test of copper halide with bluish-green color identifies the presence of:
🟩 A. Halogen
🟪 B. Hydrogen
🟨 C. ✔️ Copper (Cu²⁺)
🟦 D. b and c
18. Spectroscopy is the interaction of light with:
🟩 A. Liquid
🟪 B. Solid
🟨 C. Gas
🟦 D. ✔️ Matter
19. Which type of bond is formed between H₂O molecules?
🟩 A. ✔️ Hydrogen bond
🟪 B. Ionic bond
🟨 C. Covalent bond
🟦 D. All of these
20. Soaps is the term for a salt of a:
🟩 A. Carboxylic acid
🟪 B. Citric acid
🟨 C. Sulphuric acid
🟦 D. ✔️ Fatty acid
21. The use of potassium hydroxide produces a:
🟩 A. Hard soap
🟪 B. ✔️ Soft soap
🟨 C. Moderate soap
🟦 D. All of these
22. Citric acid is used in preparation of cold drinks for:
🟩 A. Sweet taste
🟪 B. Bitter taste
🟨 C. ✔️ Sour taste
🟦 D. Salty taste
23. The value of Kc increases when:
🟩 A. [Reactant] = [Product]
🟪 B. [Product] is less
🟨 C. [Reactant] is less ✔️
🟦 D. [Product] is less
24. Which of the following represents backward reaction?
🟩 A. (i) and (ii)
🟪 B. ✔️ (ii) only
🟨 C. (i) only
🟦 D. (iii) only
25. If pH value is greater than 7, the solution is:
🟩 A. Acidic
🟪 B. ✔️ Basic
🟨 C. Amphotetic
🟦 D. Neutral
26. Polyethene is:
🟩 A. Oil
🟪 B. Paper
🟨 C. ✔️ Plastic
🟦 D. Wood
27. Fresh water present on the surface of Earth is:
🟩 A. 0.3%
🟪 B. ✔️ 3%
🟨 C. 0.2%
🟦 D. 2%
28. The gas is the mobile phase in:
🟩 A. Liquid chromatography
🟪 B. Solid chromatography
🟨 C. ✔️ Gas chromatography
🟦 D. None of these
29. Deficiency of which vitamin causes scurvy?
🟩 A. D
🟪 B. ✔️ C
🟨 C. B
🟦 D. A
30. Water covers around ………… % of Earth’s surface:
🟩 A. 50
🟪 B. 60
🟨 C. ✔️ 70
🟦 D. 80
31. Water is:
🟩 A. Acidic and polar
🟪 B. Neutral and non-polar
🟨 C. Acidic and non-polar
🟦 D. ✔️ Neutral and polar
32. Which of the following is a Lewis acid?
🟩 A. HCl
🟪 B. HNO₃
🟨 C. NH₃
🟦 D. ✔️ AlCl₃
33. Fructose is:
🟩 A. Fruit sugar
🟪 B. Honey sugar
🟨 C. Ketose sugar
🟦 D. ✔️ All of these
34. The functional group –CHO is used for:
🟩 A. Carboxylic acid
🟪 B. ✔️ Aldehyde
🟨 C. Ketone
🟦 D. Alcohol
35. Rickets is caused by deficiency of:
🟩 A. Vitamin A
🟪 B. ✔️ Vitamin D
🟨 C. Vitamin C
🟦 D. Vitamin E
36. The pH of 1.0 M HCl solution is:
🟩 A. ✔️ 0
🟪 B. 1
🟨 C. 2
🟦 D. 7
37. Arrhenius theory is applicable in:
🟩 A. ✔️ Aqueous solution
🟪 B. Non-aqueous solution
🟨 C. Both of them
🟦 D. Binary solution
38. The IUPAC name of iso-pentane is:
🟩 A. ✔️ 2,2-Dimethylbutane
🟪 B. 2-Methylpentane
🟨 C. 2,2-Dimethylpropane
🟦 D. 2-Methylbutane
39. Glycogen is an example of:
🟩 A. Monosaccharide
🟪 B. Oligosaccharide
🟨 C. Disaccharide
🟦 D. ✔️ Polysaccharide
40. End point of titration can be determined by:
🟩 A. HPLC
🟪 B. Potentiometry
🟨 C. Conductometry
🟦 D. ✔️ All of these
41. The name vitamin was coined by:
🟩 A. J. Wöhler
🟪 B. Watson and Crick
🟨 C. Hopkins
🟦 D. ✔️ Funk
42. Which of the following is NOT an example of neutral salt?
🟩 A. KCl
🟪 B. K₂SO₄
🟨 C. ✔️ K₂CO₃
🟦 D. KNO₃
43. The unit of Kc for reaction: Fe³⁺ + 4Cl⁻ → FeCl₄⁻
🟩 A. ✔️ mol⁻¹ dm³
🟪 B. mol⁻⁴ dm¹²
🟨 C. mol⁻² dm¹⁶
🟦 D. mol⁴ dm¹²
44. The pH of black coffee is:
🟩 A. 7.0
🟪 B. ✔️ 5.0
🟨 C. 13.0
🟦 D. 7.35
45. Deficiency of vitamin K leads to:
🟩 A. Scurvy
🟪 B. Haemolysis
🟨 C. ✔️ Hemorrhage
🟦 D. Rickets
46. Which of the following pair of compounds does not belong to the same homologous series?
🟩 A. C₂H₄ & C₃H₆
🟪 B. CH₄ & C₂H₆
🟨 C. C₂H₅OH & C₃H₇OH
🟦 D. ✔️ C₂H₂ & C₃H₈
47. Which of the following pair of compounds does not differ by –CH₂– group?
🟩 A. C₉H₂₀ & C₁₀H₂₂
🟪 B. C₂H₅ & C₃H₇
🟨 C. C₂H₅Cl & C₃H₇Cl
🟦 D. ✔️ C₂H₂ & C₂H₄
48. Which of the following is NOT used in the preparation of soft drinks?
🟩 A. Water
🟪 B. Sucrose
🟨 C. ✔️ Fatty acid
🟦 D. Citric acid
49. This is known as blood sugar:
🟩 A. Fructose
🟪 B. ✔️ Glucose
🟨 C. Lactose
🟦 D. Maltose
50. This one of the following is used as jet aircraft fuel?
🟩 A. Fuel oil
🟪 B. Diesel oil
🟨 C. ✔️ Kerosene oil
🟦 D. Petrol
51. The closeness between the measured value and the true value of an observation is called:
🟩 A. ✔️ Accuracy
🟪 B. Precision
🟨 C. Difference
🟦 D. Error
52. The ordinary IR region extends from …………… wavelength (µm):
🟩 A. ✔️ 2.5–15
🟪 B. 2.6–15
🟨 C. 2.7–15
🟦 D. 2.8–15
53. Atmospheric pressure decreases with the:
🟩 A. Increase in longitude
🟪 B. Decrease in altitude
🟨 C. ✔️ Increase in altitude
🟦 D. None
✅ Answer Key with Short Reasons
1 A Kc = [products]^coeff / [reactants]^coeff.
2 A Δn ≠ 0; Kc has units when moles of products ≠ reactants.
3 B SO₂ is not a proton donor, so not Arrhenius acid.
4 A Amphoteric substances react with both acids & bases.
5 B Saturated hydrocarbons contain only single C–C bonds.
6 C CH₃–CH₂–CH₂– = n-propyl radical.
7 B Surfactants lower water’s surface tension.
8 C Hydrophilic end is polar, interacts with water.
9 C Lactose = milk sugar (glucose + galactose).
10 B Stratosphere: 50–55 km above Earth’s surface.
11 A Tropopause separates troposphere & stratosphere.
12 D O₂ is not a greenhouse gas.
13 D Bitumen is used in road surfacing.
14 C Alkyl radical: CₙH₂ₙ₊₁.
15 C CO₂ absorbs IR radiation, contributing to greenhouse effect.
16 A Permanent hardness is due to Mg²⁺/Ca²⁺ salts (e.g., MgSO₄).
17 C Bluish-green flame confirms presence of Cu²⁺.
18 D Spectroscopy studies light-matter interactions.
19 A H-bonds form between H₂O molecules.
20 D Soaps are salts of fatty acids.
21 B KOH produces soft soap due to solubility of potassium salts.
22 C Citric acid gives sour taste in beverages.
23 C Kc increases when reactant concentration is less.
24 B Backward reaction is represented by the reverse arrow (ii).
25 B pH > 7 indicates basic solution.
26 C Polyethene is a plastic polymer.
27 B Only ~3% of water on Earth is fresh water.
28 C In gas chromatography, gas acts as the mobile phase.
29 B Vitamin C deficiency causes scurvy.
30 C ~70% of Earth's surface is covered with water.
31 D Water is neutral (pH ~7) and polar due to H–O–H structure.
32 D Lewis acid accepts an electron pair; AlCl₃ is electron-deficient.
33 D Fructose is found in fruits, honey, and is a ketose sugar.
34 B –CHO is the functional group for aldehydes.
35 B Lack of Vitamin D causes rickets (soft bones).
36 A pH = −log[H⁺] = 0 for 1 M HCl.
37 A Arrhenius theory applies to aqueous solutions only.
38 A Iso-pentane’s IUPAC name is 2,2-dimethylbutane.
39 D Glycogen is a polysaccharide (many glucose units).
40 C End point can be determined by multiple methods: HPLC, potentiometry, or conductometry
41 D Funk coined the term “vitamine” for essential amines.
42 C K₂CO₃ is basic, not neutral.
43 A For Fe³⁺ + 4Cl⁻ → FeCl₄⁻, Kc unit = mol⁻¹ dm³.
44 B Black coffee is acidic, pH ~5.
45 C Vitamin K deficiency causes hemorrhage (blood clotting issues).
46 D C₂H₂ (alkyne) & C₃H₈ (alkane) are different homologous series.
47 D C₂H₂ & C₂H₄ differ by a double bond, not –CH₂– group.
48 C Fatty acids are not used in soft drinks.
49 B Glucose is blood sugar.
50 C Kerosene oil is used as jet fuel.
51 A Accuracy measures closeness to the true value.
52 A Ordinary IR region is 2.5–15 µm.
53 C Atmospheric pressure decreases with increasing altitude.
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