Q1. Heating lead nitrate produces brown fumes of:
A. Nitric oxide ❌
B. Nitrogen monoxide ❌
C. Nitrogen dioxide ✅
D. Nitrous oxide ❌
Why correct: Nitrogen dioxide is brown.
Why others wrong: The others are colorless gases.
Q2. Brown coloured gas NO₂ is:
A. Nitrous oxide ❌
B. Nitrogen monoxide ❌
C. Nitrogen dioxide ✅
D. Nitric oxide ❌
Why correct: NO₂ is brown in color.
Why others wrong: The others are not brown gases.
Q3. Lead nitrate on heating gives:
A. PbS, NO₂, O₂ ❌
B. PbO, NO₂, O₂ ✅
C. PbCl₂, CO₂, O₂ ❌
D. PbO, H₂O, NO₂ ❌
Why correct: Decomposition of lead nitrate yields PbO, NO₂, and O₂.
Why others wrong: They do not form these products.
Q4. Chemical formula of lead nitrate is:
A. PbO ❌
B. Pb(NO₃)₂ ✅
C. PbCO₃ ❌
D. PbSO₄ ❌
Why correct: The formula for lead nitrate is Pb(NO₃)₂.
Why others wrong: They are other lead compounds.
Q5. Lead oxide remains as:
A. Gas ❌
B. Liquid ❌
C. Solid ✅
D. Aqueous ❌
Why correct: Lead oxide is a solid.
Why others wrong: It does not form as gas, liquid, or solution.
Q6. O₂ obtained in decomposition is:
A. Nitrogen ❌
B. Hydrogen ❌
C. Oxygen ✅
D. Carbon dioxide ❌
Why correct: Decomposition of lead nitrate releases oxygen.
Why others wrong: They are not released in this reaction.
Q7. Heating Pb(NO₃)₂ is an example of:
A. Combination reaction ❌
B. Displacement reaction ❌
C. Decomposition reaction ✅
D. Neutralization reaction ❌
Why correct: It breaks down into simpler substances.
Why others wrong: They do not describe decomposition.
Q8. Decomposition of lead nitrate requires:
A. Electricity ❌
B. Light ❌
C. Heat ✅
D. Pressure ❌
Why correct: Heat is needed for decomposition.
Why others wrong: The other methods are not used here.
Q9. Electrolysis breaks water into:
A. Oxygen and nitrogen ❌
B. Hydrogen and oxygen ✅
C. Carbon dioxide and oxygen ❌
D. Carbon monoxide and hydrogen ❌
Why correct: Electrolysis of water produces hydrogen and oxygen.
Why others wrong: They do not form these gases.
Q10. The electrodes used in Activity 5.7 are made of:
A. Copper ❌
B. Zinc ❌
C. Carbon ✅
D. Silver ❌
Why correct: Carbon electrodes are commonly used.
Why others wrong: They are not suitable here.
Q11. Battery used in electrolysis is of:
A. 3 volt ❌
B. 9 volt ❌
C. 6 volt ✅
D. 12 volt ❌
Why correct: A 6-volt battery is standard for this setup.
Why others wrong: They are not typically used.
Q12. Why dilute sulphuric acid is added?
A. Increase colour ❌
B. Increase volume ❌
C. Increase conductivity ✅
D. Increase smell ❌
Why correct: Acid increases the solution’s conductivity.
Why others wrong: They do not serve this purpose.
Q13. Which gas collects in double amount?
A. Oxygen ❌
B. Nitrogen ❌
C. Hydrogen ✅
D. Carbon dioxide ❌
Why correct: Hydrogen is produced in double the volume compared to oxygen.
Why others wrong: They do not follow the ratio.
Q14. Volume of hydrogen is double because:
A. It is lighter ❌
B. Equation ratio is 2:1 ✅
C. It reacts faster ❌
D. It dissolves ❌
Why correct: The ratio of gases in water electrolysis is 2:1.
Why others wrong: They are incorrect reasons.
Q15. Gas at cathode is:
A. Oxygen ❌
B. Nitrogen ❌
C. Hydrogen ✅
D. Carbon dioxide ❌
Why correct: Hydrogen is produced at the cathode.
Why others wrong: They are not formed at the cathode.
Q16. Gas at anode is:
A. Nitrogen ❌
B. Oxygen ✅
C. Hydrogen ❌
D. Chlorine ❌
Why correct: Oxygen is produced at the anode.
Why others wrong: They are not formed at the anode.
Q17. Burning candle test confirms presence of:
A. Nitrogen ❌
B. CO₂ ❌
C. Hydrogen and oxygen ✅
D. Ammonia ❌
Why correct: The test confirms both hydrogen and oxygen.
Why others wrong: They are not confirmed by this test.
Q18. Silver chloride turns grey due to:
A. Oxidation ❌
B. Reduction ❌
C. Photochemical decomposition ✅
D. Precipitation ❌
Why correct: Light causes silver chloride to decompose.
Why others wrong: They do not explain the color change.
Q19. Colour of silver chloride is:
A. Brown ❌
B. Grey ❌
C. White ✅
D. Blue ❌
Why correct: Silver chloride is white.
Why others wrong: They are incorrect colors.
Q20. Decomposition of AgCl occurs due to:
A. Heat ❌
B. Electricity ❌
C. Light ✅
D. Pressure ❌
Why correct: Light causes the decomposition.
Why others wrong: They do not trigger this reaction.
Q21. Product of silver chloride decomposition includes:
A. Ag and Cl₂ ✅
B. Ag₂O and Cl₂ ❌
C. AgO and Cl ❌
D. Ag and HCl ❌
Why correct: Silver chloride breaks down into silver and chlorine gas.
Why others wrong: They do not form these products.
Q22. Silver bromide behaves like:
A. Sodium chloride ❌
B. Silver chloride ✅
C. Copper sulphate ❌
D. Barium sulphate ❌
Why correct: Silver bromide and silver chloride have similar properties.
Why others wrong: They are not similar.
Q23. AgBr on light gives:
A. Ag + Br₂ ✅
B. AgO + Br₂ ❌
C. Ag + O₂ ❌
D. Ag₂O + Br₂ ❌
Why correct: Silver bromide decomposes into silver and bromine.
Why others wrong: They are incorrect reactions.
Q24. Photographic films use:
A. Lead nitrate ❌
B. Silver salts ✅
C. Iron oxide ❌
D. Zinc oxide ❌
Why correct: Silver salts are used in photographic films.
Why others wrong: They are not used for photography.
Q25. These reactions are examples of:
A. Thermal decomposition ❌
B. Electrolysis ❌
C. Photochemical decomposition ✅
D. Displacement ❌
Why correct: They involve light-induced decomposition.
Why others wrong: They do not match this process.
Q26. Reactions which absorb heat are:
A. Exothermic ❌
B. Endothermic ✅
C. Physical ❌
D. Nuclear ❌
Why correct: Endothermic reactions absorb heat.
Why others wrong: They release heat or are unrelated.
Q27. Energy required in decomposition may be in form of:
A. Water only ❌
B. Heat only ❌
C. Heat, light or electricity ✅
D. Pressure only ❌
Why correct: Decomposition can require various forms of energy.
Why others wrong: They are too limited.
Q28. Barium hydroxide and ammonium chloride reaction feels:
A. Hot ❌
B. Neutral ❌
C. Cold ✅
D. Warm ❌
Why correct: This reaction is endothermic and feels cold.
Why others wrong: They do not describe the correct temperature change.
Q29. Reaction of Ba(OH)₂ and NH₄Cl is:
A. Exothermic ❌
B. Endothermic ✅
C. Combination ❌
D. Decomposition ❌
Why correct: It absorbs heat and is endothermic.
Why others wrong: They do not describe this reaction correctly.
Q30. Brown coating on iron nail is due to:
A. Iron oxide ❌
B. Copper ✅
C. Zinc ❌
D. Lead ❌
Why correct: Copper displaces iron, causing a brown coating.
Why others wrong: They are not involved in this process.
Q31. Blue solution fades because:
A. Iron decomposes ❌
B. Copper displaces iron ❌
C. Iron displaces copper ✅
D. Copper evaporates ❌
Why correct: Iron displaces copper, causing the blue color to fade.
Why others wrong: They do not explain the fading.
Q32. Reaction Fe + CuSO₄ gives:
A. FeSO₄ + Cu ✅
B. CuSO₄ + Fe ❌
C. Fe + Cu ❌
D. Fe₂O₃ ❌
Why correct: Iron displaces copper from copper sulfate.
Why others wrong: They do not match the reaction.
Q33. Iron nail becomes brown as:
A. FeO forms ❌
B. Copper deposits ❌
C. Rust forms ✅
D. Lead forms ❌
Why correct: Iron forms rust, turning brown.
Why others wrong: They are not correct explanations.
Q34. More reactive metal is:
A. Copper ❌
B. Iron ✅
C. Silver ❌
D. Gold ❌
Why correct: Iron is more reactive than copper.
Why others wrong: They are less reactive.
Q35. Zn displaces Cu because:
A. Zn is heavier ❌
B. Zn is more reactive ✅
C. Zn is softer ❌
D. Zn is liquid ❌
Why correct: Zinc is more reactive than copper.
Why others wrong: They do not explain the displacement.
Q36. Pb displaces copper because:
A. Pb is noble ❌
B. Pb is heavy ❌
C. Pb is more reactive ✅
D. Pb is liquid ❌
Why correct: Lead is more reactive than copper.
Why others wrong: They do not justify the displacement.
Q37. Type of reaction Fe + CuSO₄ is:
A. Combination ❌
B. Displacement ✅
C. Decomposition ❌
D. Redox ❌
Why correct: Iron displaces copper in the reaction.
Why others wrong: They do not match the reaction type.
Q38. Zn + CuSO₄ is example of:
A. Decomposition ❌
B. Combination ❌
C. Displacement ✅
D. Precipitation ❌
Why correct: Zinc displaces copper in the reaction.
Why others wrong: They do not describe this process.
Q39. Na₂SO₄ + BaCl₂ forms:
A. BaSO₄ + NaCl ✅
B. BaSO₄ + HCl ❌
C. Na₂SO₄ only ❌
D. NaCl only ❌
Why correct: Barium sulfate precipitates, and sodium chloride remains in solution.
Why others wrong: They do not form these products.
Q40. White precipitate is:
A. BaCl₂ ❌
B. Na₂SO₄ ❌
C. BaSO₄ ✅
D. NaCl ❌
Why correct: Barium sulfate is the white precipitate.
Why others wrong: They do not form a precipitate.
Q41. Precipitate is:
A. Gas ❌
B. Liquid ❌
C. Insoluble solid ✅
D. Solution ❌
Why correct: A precipitate is an insoluble solid.
Why others wrong: They are not precipitates.
Q42. Exchange of ions occurs in:
A. Combination ❌
B. Decomposition ❌
C. Displacement ❌
D. Double displacement ✅
Why correct: Double displacement involves ion exchange.
Why others wrong: They do not involve ion exchange.
Q43. Lead nitrate and potassium iodide produce:
A. White ppt ❌
B. Yellow ppt ✅
C. Blue ppt ❌
D. Green ppt ❌
Why correct: Lead iodide is yellow.
Why others wrong: They do not form a yellow precipitate.
Q44. Compound formed is:
A. PbCl₂ ❌
B. PbI₂ ✅
C. PbSO₄ ❌
D. PbCO₃ ❌
Why correct: Lead iodide is formed.
Why others wrong: They are incorrect compounds.
Q45. KI + Pb(NO₃)₂ is:
A. Combination ❌
B. Double displacement ✅
C. Displacement ❌
D. Decomposition ❌
Why correct: It is a double displacement reaction.
Why others wrong: They do not match the reaction type.
Q46. Heating copper forms:
A. Cu₂O ❌
B. CuO ✅
C. CuCO₃ ❌
D. CuCl₂ ❌
Why correct: Heating copper in air forms copper oxide.
Why others wrong: They are not the correct products.
Q47. Copper gains:
A. Nitrogen ❌
B. Hydrogen ❌
C. Oxygen ✅
D. Chlorine ❌
Why correct: Copper reacts with oxygen.
Why others wrong: They do not match the reaction.
Q48. Copper is:
A. Reduced ❌
B. Oxidized ✅
C. Decomposed ❌
D. Displaced ❌
Why correct: Copper is oxidized when it forms oxide.
Why others wrong: They do not describe this process.
Q49. CuO + H₂ forms:
A. Cu + H₂O ✅
B. CuO₂ ❌
C. Cu + O₂ ❌
D. Cu + H₂ ❌
Why correct: Copper oxide is reduced to copper and water.
Why others wrong: They do not match the reaction.
Q50. CuO loses oxygen, so it is:
A. Oxidized ❌
B. Reduced ✅
C. Displaced ❌
D. Combined ❌
Why correct: The loss of oxygen means copper oxide is reduced.
Why others wrong: They do not match the process.
Q51. Which one must be balanced first?
A. Simple element ❌
B. Compound with maximum atoms ✅
C. Gas ❌
D. Liquid ❌
Why correct: Complex compounds are balanced first to simplify the process.
Why others wrong: They don’t prioritize complexity.
Q52. Fe₃O₄ has how many oxygen atoms?
A. 2 ❌
B. 3 ❌
C. 4 ✅
D. 5 ❌
Why correct: The subscript 4 indicates four oxygen atoms.
Why others wrong: They miscount the atoms.
Q53. In Fe + H₂O → Fe₃O₄ + H₂, initial Fe atoms are:
A. 1 ✅
B. 2 ❌
C. 3 ❌
D. 4 ❌
Why correct: The equation starts with one iron atom.
Why others wrong: They do not match the initial count.
Q54. After balancing iron atoms become:
A. 1 ❌
B. 2 ❌
C. 3 ✅
D. 4 ❌
Why correct: Balanced equation shows three iron atoms.
Why others wrong: They do not match the balanced count.
Q55. Hydrogen atoms in 4H₂O are:
A. 2 ❌
B. 4 ❌
C. 6 ❌
D. 8 ✅
Why correct: Each H₂O has 2 hydrogen atoms, so 4 molecules have 8.
Why others wrong: They miscount the hydrogen atoms.
Q56. Correct number of H₂ after balancing is:
A. 1 ❌
B. 2 ❌
C. 3 ❌
D. 4 ✅
Why correct: After balancing, there are four hydrogen molecules.
Why others wrong: They do not match the balanced count.
Q57. Balanced form of iron reaction is:
A. Fe + H₂O → Fe₃O₄ ❌
B. 3Fe + 4H₂O → Fe₃O₄ + 4H₂ ✅
C. Fe₃O₄ → Fe ❌
D. Fe + O₂ → FeO ❌
Why correct: This is the balanced equation showing correct stoichiometry.
Why others wrong: They do not balance properly.
Q58. What does (aq) stand for?
A. Air quality ❌
B. Aqueous ✅
C. Atom quantity ❌
D. Acid quantity ❌
Why correct: (aq) means a substance dissolved in water.
Why others wrong: They are not related to chemistry states.
Q59. (g) in chemical equation means:
A. Green ❌
B. Gas ✅
C. Gravity ❌
D. Group ❌
Why correct: (g) stands for gas.
Why others wrong: They do not represent a physical state.
Q60. Which reaction gives white powder?
A. Zinc and acid ❌
B. Magnesium burning ✅
C. Iron rusting ❌
D. Lead reaction ❌
Why correct: Magnesium burning forms a white powder (magnesium oxide).
Why others wrong: They do not produce a white powder.
Q61. Chemical equation written in words is called:
A. Molecular equation ❌
B. Word equation ✅
C. Skeletal equation ❌
D. Balanced equation ❌
Why correct: A word equation uses names rather than symbols.
Why others wrong: They refer to different types of equations.
Q62. Chemical formula makes equation:
A. Longer ❌
B. Confusing ❌
C. Shorter and clearer ✅
D. Useless ❌
Why correct: Formulas make equations more concise and clear.
Why others wrong: They do not enhance clarity.
Q63. Which state symbol is for solid?
A. (s) ✅
B. (aq) ❌
C. (g) ❌
D. (l) ❌
Why correct: (s) indicates a solid state.
Why others wrong: They represent different states.
Q64. What happens if mass changes?
A. Reaction complete ❌
B. Law violated ✅
C. Product formed ❌
D. Reaction reversed ❌
Why correct: A change in mass indicates violation of the conservation of mass.
Why others wrong: They do not address the law of conservation.
Q65. Which one is not a sign of chemical reaction?
A. Gas evolution ❌
B. Colour change ❌
C. Ice melting ✅
D. Temperature change ❌
Why correct: Ice melting is a physical change, not chemical.
Why others wrong: They indicate chemical changes.
Q66. Which step comes first in balancing equations?
A. Count atoms ❌
B. Box formulas ✅
C. Multiply ❌
D. Remove atoms ❌
Why correct: Boxing the formulas helps organize the equation first.
Why others wrong: They are later steps.
Q67. Second step in balancing is:
A. Writing product ❌
B. Listing atom numbers ✅
C. Adding coefficients ❌
D. Heating ❌
Why correct: Listing atom numbers helps identify imbalance.
Why others wrong: They are not initial steps.
Q68. Balancing oxygen first is chosen because:
A. It is gas ❌
B. Highest number of atoms ✅
C. It is liquid ❌
D. It is easy ❌
Why correct: Oxygen often appears in greater quantity.
Why others wrong: They do not explain the reason.
Q69. Why formulas cannot be changed?
A. They are imaginary ❌
B. They fix atom ratio ✅
C. They are random ❌
D. They change mass ❌
Why correct: Formulas define the exact ratio of atoms.
Why others wrong: They do not maintain this ratio.
Q70. Which is wrong while balancing?
A. Changing subscripts ✅
B. Adding coefficients ❌
C. Counting atoms ❌
D. Using trials ❌
Why correct: Changing subscripts alters the compound.
Why others wrong: