CIE iGCSE Co-Ordinated Science C6.3 Redox Exam Style Questions Paper 1
Question
Which reaction is not a redox reaction?
A iron oxide + carbon iron + carbon dioxide
B silver nitrate + sodium chloride silver chloride + sodium nitrate
C copper oxide + hydrogen copper + water
D magnesium + oxygen magnesium oxide
▶️Answer/Explanation
Ans :A
Question
Which word equation represents a redox reaction?
A calcium carbonate → calcium oxide + carbon dioxide
B calcium oxide + hydrochloric acid → calcium chloride + water
C copper oxide + carbon → copper + carbon dioxide
D sodium oxide + water → sodium hydroxide
▶️Answer/Explanation
Ans : C
Question
Which statement shows that methane, CH4, is oxidised when it burns?
(A) The products of the reaction are gaseous.
(B) The products of the reaction are water and carbon dioxide.
(C) The reaction is exothermic.
(D) The total number of oxygen atoms has increased during the reaction.
▶️Answer/Explanation
Ans : B
Question
In which change is the oxide of phosphorus, P2O3, reduced?
▶️Answer/Explanation
Ans: A
Question
When petrol burns in a car engine, carbon monoxide, CO, and nitrogen monoxide, NO, are produced.
These gases pass through a catalytic converter where carbon monoxide reacts with nitrogen monoxide.
The equation for the reaction is shown.
carbon monoxide + nitrogen monoxide → nitrogen + carbon dioxide
Which statement is not correct?
(A) Carbon monoxide is oxidised in the catalytic converter.
(B) Carbon monoxide is produced by the complete combustion of petrol.
(C) Nitrogen from the air is oxidised in the car engine.
(D) Nitrogen monoxide is reduced in the catalytic converter.
▶️Answer/Explanation
Ans : B
Question
Which statement explains why the rusting of iron is an oxidation reaction?
A Iron gains oxygen.
B Iron is a transition element.
C Iron is very reactive.
D Iron loses oxygen.
▶Answer/Explanation
Ans : A
Question
Which reactions involve oxidation?
1. C + O2 → CO2
2. 2NaOH + H2SO4 → Na2SO4 + 2H2O
3. 2Mg + O2 → 2MgO
4. CaCO3 → CaO + CO2
(A) 1 and 3 (B) 1 and 4 (C) 2 and 3 (D) 2 and 4
▶️Answer/Explanation
Ans: A
Question
The equation for the reaction between iron(III) oxide, Fe2O3, and carbon is shown.
\( 2Fe_{2}O_{3} + 3C \to 4Fe +3 CO_{2}\)
Which statement about this reaction is correct?
(A) C is oxidised.
(B) CO2 is reduced.
(C) Fe is oxidised.
(D) Fe2O3 is oxidised.
▶️Answer/Explanation
Ans: A
Question
Which statement about oxidation is correct?
(A) It occurs when an element or compound chemically combines with oxygen.
(B) It occurs when an element or compound forms a mixture with oxygen.
(C) It occurs when an element or compound is separated from a mixture with oxygen.
(D) It occurs when a compound loses oxygen.
▶️Answer/Explanation
Ans: A
Question
In which equation is the underlined substance acting as an oxidising agent?
A. CuO + H₂ → Cu + H₂O
B. CuSO₄ + Mg → MgSO₄ + Cu
C. H₂ + Cl₂ → 2HCl
D. Zn + 2HCl → ZnCl₂ + H₂
▶️Answer/Explanation
Answer: C. H₂ + Cl₂ → 2HCl
Explanation: In the reaction H₂ + Cl₂ → 2HCl, chlorine (Cl₂) is acting as an oxidising agent because it gains electrons from hydrogen, causing hydrogen to be oxidised.
Question
Which word equation represents a redox reaction?
A. carbon + copper oxide → copper + carbon dioxide
B. hydrochloric acid + potassium hydroxide → potassium chloride + water
C. magnesium carbonate → magnesium oxide + carbon dioxide
D. sodium sulfate + barium nitrate → barium sulfate + sodium nitrate
▶️Answer/Explanation
Answer: A. carbon + copper oxide → copper + carbon dioxide
Explanation: This is a redox reaction because carbon is oxidized to carbon dioxide, and copper oxide is reduced to copper.
Question
The catalytic converter in the exhaust of a car brings about the reaction shown.
2NO + 2CO → 2CO₂ + N₂
Which row about this reaction is correct?
| Option | Oxidation | Reduction |
|---|---|---|
| A | ✓ | ✓ |
| B | ✓ | ✗ |
| C | ✗ | ✓ |
| D | ✗ | ✗ |
▶️Answer/Explanation
Answer: A
Explanation: In this reaction, CO is oxidized to CO₂, and NO is reduced to N₂. Therefore, both oxidation and reduction occur.
Question
Which reaction involves both oxidation and reduction?
A. calcium carbonate → calcium oxide + carbon dioxide
B. copper oxide + carbon → copper + carbon dioxide
C. silver nitrate + potassium chloride → silver chloride + potassium nitrate
D. sulfuric acid + sodium hydroxide → sodium sulfate + water
▶️Answer/Explanation
Answer: B. copper oxide + carbon → copper + carbon dioxide
Explanation: In this reaction, copper oxide is reduced to copper, and carbon is oxidized to carbon dioxide. Therefore, both oxidation and reduction occur.
Question
Which statement explains why the rusting of iron is an oxidation reaction?
A. Iron gains oxygen.
B. Iron is a transition metal.
C. Iron is very reactive.
D. Iron loses oxygen.
▶️Answer/Explanation
Answer: A. Iron gains oxygen.
Explanation: Rusting is an oxidation reaction because iron reacts with oxygen in the presence of water to form iron oxide (rust). In this process, iron gains oxygen, which is characteristic of oxidation.
Question
In which reaction is zinc being oxidised?
- 2Zn + O2 → 2ZnO
- ZnO + Mg → Zn + MgO
- Zn + CuO → ZnO + Cu
A. 1 and 2 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2 and 3
▶️Answer/Explanation
Answer: B
Explanation: In reactions 1 and 3, zinc (Zn) loses electrons and is oxidized to form zinc oxide (ZnO). In reaction 2, zinc is reduced, not oxidized.