Q1. A substance is oxidised if it:
A. Gains hydrogen ❌
B. Loses oxygen ❌
C. Gains oxygen ✅
D. Gains water ❌
Why correct: Oxidation means gain of oxygen.
Why others wrong: Gaining hydrogen or losing oxygen means reduction; water has no role.
Q2. A substance is reduced if it:
A. Gains oxygen ❌
B. Loses oxygen ✅
C. Gains nitrogen ❌
D. Gains carbon ❌
Why correct: Reduction means loss of oxygen.
Why others wrong: Gaining oxygen means oxidation; nitrogen and carbon are not definitions.
Q3. Oxidation can also be defined as:
A. Gain of oxygen or loss of hydrogen ✅
B. Loss of oxygen or gain of hydrogen ❌
C. Gain of nitrogen ❌
D. Loss of carbon ❌
Why correct: Either gaining oxygen or losing hydrogen = oxidation.
Why others wrong: These define reduction or are incorrect.
Q4. Reduction involves:
A. Gain of oxygen ❌
B. Loss of hydrogen ❌
C. Loss of oxygen ✅
D. Gain of carbon ❌
Why correct: Reduction means removal of oxygen.
Why others wrong: Gain of oxygen and loss of hydrogen indicate oxidation.
Q5. Magnesium burns to form:
A. Magnesium chloride ❌
B. Magnesium oxide ✅
C. Magnesium nitrate ❌
D. Magnesium sulphate ❌
Why correct: Magnesium reacts with oxygen to give MgO.
Why others wrong: These require chlorine, nitrogen, or sulphur.
Q6. Burning of magnesium ribbon shows magnesium is:
A. Reduced ❌
B. Oxidised ✅
C. Displaced ❌
D. Neutralised ❌
Why correct: Magnesium gains oxygen, so it is oxidised.
Why others wrong: No loss of oxygen, no displacement, no acid-base reaction.
Q7. White substance formed on burning magnesium is:
A. MgCl₂ ❌
B. MgCO₃ ❌
C. MgO ✅
D. Mg(NO₃)₂ ❌
Why correct: Magnesium oxide is white in colour.
Why others wrong: Those contain different elements.
Q8. In oxidation-reduction reactions:
A. Only oxidation occurs ❌
B. Only reduction occurs ❌
C. Both occur together ✅
D. Only displacement occurs ❌
Why correct: Oxidation and reduction always happen simultaneously.
Why others wrong: One cannot occur alone.
CORROSION
Q9. Rusting of iron is called:
A. Oxidation ❌
B. Electrolysis ❌
C. Corrosion ✅
D. Rancidity ❌
Why correct: Rusting is corrosion of iron.
Why others wrong: Others are different processes.
Q10. Colour of rust is:
A. Blue ❌
B. Black ❌
C. Reddish-brown ✅
D. Green ❌
Why correct: Rust appears reddish-brown.
Why others wrong: Those are different colours.
Q11. Iron corrodes due to attack of:
A. Oxygen only ❌
B. Moisture only ❌
C. Acids only ❌
D. Moisture, acids etc. ✅
Why correct: Moisture and air together cause corrosion.
Why others wrong: No single factor causes rusting alone.
Q12. Black coating forms on:
A. Iron ❌
B. Silver ✅
C. Aluminium ❌
D. Zinc ❌
Why correct: Silver forms black tarnish.
Why others wrong: These form different coatings.
Q13. Green coating forms on:
A. Copper ✅
B. Iron ❌
C. Zinc ❌
D. Lead ❌
Why correct: Copper develops green patina.
Why others wrong: Other metals form other coloured oxides.
Q14. Which metal tarnishes black?
A. Iron ❌
B. Copper ❌
C. Silver ✅
D. Zinc ❌
Why correct: Silver forms black silver sulphide.
Why others wrong: They do not tarnish black.
Q15. Corrosion causes damage to:
A. Car bodies ❌
B. Railings ❌
C. Bridges ❌
D. All of these ✅
Why correct: Corrosion damages all metal structures.
Why others wrong: All are affected.
Q16. Rusting of iron is a:
A. Physical change ❌
B. Chemical change ✅
C. Nuclear change ❌
D. Temporary change ❌
Why correct: A new substance (rust) is formed.
Why others wrong: It is permanent and chemical.
Q17. Money is spent yearly due to:
A. Galvanisation ❌
B. Combustion ❌
C. Corrosion ✅
D. Electrolysis ❌
Why correct: Rust damage costs money to repair.
Why others wrong: They are not the main causes of loss.
RANCIDITY
Q18. Fats become rancid due to:
A. Reduction ❌
B. Oxidation ✅
C. Hydrolysis ❌
D. Electrolysis ❌
Why correct: Fat reacts with oxygen and spoils.
Why others wrong: They are unrelated.
Q19. Rancidity affects:
A. Colour only ❌
B. Shape only ❌
C. Taste and smell ✅
D. Weight only ❌
Why correct: Rancid food smells bad and tastes bad.
Why others wrong: Other changes are not main effects.
Q20. Substances that prevent oxidation are:
A. Catalysts ❌
B. Antioxidants ✅
C. Acids ❌
D. Alkalis ❌
Why correct: Antioxidants stop oxidation.
Why others wrong: They have different uses.
Q21. Airtight containers prevent:
A. Reduction ❌
B. Oxidation ✅
C. Freezing ❌
D. Evaporation ❌
Why correct: Air (oxygen) is blocked.
Why others wrong: Airtight does not freeze or reduce.
Q22. Chips packets are filled with:
A. Oxygen ❌
B. Carbon dioxide ❌
C. Nitrogen ✅
D. Hydrogen ❌
Why correct: Nitrogen prevents rancidity.
Why others wrong: Oxygen causes spoilage.
Q23. Nitrogen is used because it:
A. Reacts with food ❌
B. Prevents oxidation ✅
C. Gives smell ❌
D. Cools food ❌
Why correct: Nitrogen is inert.
Why others wrong: It does not react.
Q24. Rancidity occurs in:
A. Iron ❌
B. Water ❌
C. Cooking oil ✅
D. Salt ❌
Why correct: Oil contains fats.
Why others wrong: No fats in them.
REDOX REACTIONS
Q25. Reaction where both oxidation and reduction occur is called:
A. Neutralization ❌
B. Redox reaction ✅
C. Decomposition ❌
D. Precipitation ❌
Why correct: Redox = oxidation + reduction.
Why others wrong: They are other reaction types.
Q26. In redox reaction:
A. Only metals react ❌
B. Only heat is produced ❌
C. One is oxidised and other reduced ✅
D. Only gas is formed ❌
Why correct: Both changes occur together.
Why others wrong: Reaction is not limited this way.
Q27. In CuSO₄ and Fe reaction, copper is:
A. Oxidized ❌
B. Reduced ✅
C. Neutralized ❌
D. Dissolved ❌
Why correct: Cu²⁺ gains electrons.
Why others wrong: No oxidation or neutralisation occurs.
BALANCED EQUATIONS
Q28. A balanced equation has:
A. Equal temperature ❌
B. Equal molecules ❌
C. Equal atoms on both sides ✅
D. Equal volume ❌
Why correct: Same number of each atom.
Why others wrong: Balance is not about temperature or volume.
Q29. Balanced equations follow law of:
A. Multiple proportions ❌
B. Conservation of mass ✅
C. Definite proportions ❌
D. Constant volume ❌
Why correct: Mass is neither created nor destroyed.
Why others wrong: These apply elsewhere.
Q30. Physical states shown are:
A. s, l, g, aq ✅
B. x, y, z ❌
C. m, n, o ❌
D. b, c, d ❌
Why correct: Correct state symbols.
Why others wrong: Meaningless letters.
EXERCISE QUESTIONS
Q31. In PbO + C → Pb + CO₂, carbon is:
A. Reduced ❌
B. Oxidised ✅
C. Neutralised ❌
D. Displaced ❌
Why correct: Carbon gains oxygen.
Why others wrong: No acid-base or displacement.
Q32. In the same reaction, PbO is:
A. Oxidised ❌
B. Reduced ✅
C. Neutral ❌
D. Unchanged ❌
Why correct: PbO loses oxygen.
Why others wrong: Reaction clearly changes it.
Q33. Which statement is incorrect?
A. Pb reduced ❌
B. CO₂ oxidized ✅
C. Carbon oxidized ❌
D. PbO reduced ❌
Why correct: CO₂ is not oxidized further.
Why others wrong: They are correct.
Q34. Correct option is:
A. (a) and (b) ✅
B. (a) and (c) ❌
C. (b) only ❌
D. (d) only ❌
Why correct: Those match the correct statements.
Q35. Reaction Fe₂O₃ + Al → Al₂O₃ + Fe is:
A. Combination ❌
B. Displacement ✅
C. Decomposition ❌
D. Double displacement ❌
Why correct: Aluminium displaces iron.
Why others wrong: Only one metal is displaced.
Q36. Reaction of HCl with iron gives:
A. Iron hydroxide ❌
B. Hydrogen + iron chloride ✅
C. No reaction ❌
D. Water only ❌
Why correct: Acid reacts with metal.
Why others wrong: Products are wrong.
Q37. Hydrogen + nitrogen forms:
A. NH₃ ✅
B. NO₂ ❌
C. N₂O ❌
D. HNO₃ ❌
Why correct: Forms ammonia.
Why others wrong: Wrong compounds.
Q38. Burning of H₂S forms:
A. H₂O + SO₂ ✅
B. H₂ + S ❌
C. SO₃ + H₂ ❌
D. HCl ❌
Why correct: Combustion products.
Why others wrong: Do not match reaction.
Q39. Barium chloride reacts with aluminum sulphate to form:
A. BaSO₄ precipitate ✅
B. NaCl ❌
C. HCl ❌
D. CO₂ ❌
Why correct: White precipitate forms.
Why others wrong: Not produced here.
Q40. Potassium reacts with water to give:
A. KCl ❌
B. KOH + H₂ ✅
C. K₂O + H₂O ❌
D. KH ❌
Why correct: Strong alkali and hydrogen gas form.
Why others wrong: Wrong products.
Q41. AgNO₃ + NaCl produces:
A. NaNO₃ + AgCl ✅
B. Ag + NaCl ❌
C. Ag₂O ❌
D. HCl ❌
Why correct: Double displacement.
Why others wrong: Not formed.
Q42. BaCl₂ + H₂SO₄ produces:
A. HCl only ❌
B. BaSO₄ + HCl ✅
C. NaCl ❌
D. Ba ❌
Why correct: White precipitate forms.
Why others wrong: Missing products.
Q43. NaOH + H₂SO₄ forms:
A. Na₂SO₄ + H₂O ✅
B. NaCl ❌
C. NH₃ ❌
D. O₂ ❌
Why correct: Acid-base neutralisation.
Why others wrong: Not involved.
Q44. HNO₃ + Ca(OH)₂ produces:
A. CaCO₃ ❌
B. Ca(NO₃)₂ + H₂O ✅
C. CaCl₂ ❌
D. CaSO₄ ❌
Why correct: Salt + water formation.
Why others wrong: Wrong salt forms.
Q45. Black coating indicates:
A. Reduction ❌
B. Oxidation ✅
C. Displacement ❌
D. Electrolysis ❌
Why correct: Tarnish due to oxidation.
Why others wrong: Not happening here.
Q46. Silver tarnish is example of:
A. Rancidity ❌
B. Corrosion ✅
C. Neutralisation ❌
D. Decomposition ❌
Why correct: Slow oxidation is corrosion.
Why others wrong: Not food or acid reaction.
Q47. Green coating on copper is example of:
A. Rancidity ❌
B. Rust ❌
C. Corrosion ✅
D. Oxidation only ❌
Why correct: Copper corrodes forming green patina.
Why others wrong: Rust is only for iron.
Q48. Food becomes bad smelling due to:
A. Reduction ❌
B. Oxidation ✅
C. Neutralisation ❌
D. Electrolysis ❌
Why correct: Oxidation causes rancidity.
Why others wrong: Not related.
Q49. Antioxidants stop:
A. Reduction ❌
B. Oxidation ✅
C. Displacement ❌
D. Neutralisation ❌
Why correct: Prevent oxygen reaction.
Why others wrong: They do not affect reduction or displacement.
Q50. Nitrogen gas is used in food packing because it is:
A. Reactive ❌
B. Inert ✅
C. Toxic ❌
D. Heavy ❌
Why correct: Does not react with food.
Why others wrong: Nitrogen is neither reactive nor toxic.