CIE iGCSE Co-Ordinated Science C6.3 Redox Exam Style Questions Paper 2
▶️ Answer/Explanation
Oxidation is defined as the gain of oxygen (statement 1), while reduction is defined as the loss of oxygen (statement 4). Statement 2 incorrectly describes oxidation as loss of oxygen, and statement 3 incorrectly describes reduction as gain of oxygen. Therefore, the correct statements are 1 and 4.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
\(\text{Fe}^{2+}\) loses an electron to become \(\text{Fe}^{3+}\), so iron is oxidised.
\(\text{Cl}_2\) gains electrons to become \(\text{Cl}^-\), so chlorine is the substance reduced.
Since \(\text{Cl}_2\) accepts electrons from iron, causing iron’s oxidation, chlorine is also the oxidising agent.
✅ Answer: (A)
\(\text{Cl}_2\) gains electrons to become \(\text{Cl}^-\), so chlorine is the substance reduced.
Since \(\text{Cl}_2\) accepts electrons from iron, causing iron’s oxidation, chlorine is also the oxidising agent.
✅ Answer: (A)
▶️ Answer/Explanation
Iron (Fe) loses electrons to form \(Fe^{2+}\), so iron is oxidised.
A substance that is oxidised (loses electrons) is the reducing agent, since it causes another species to be reduced.
Here, Fe reduces \(Cu^{2+}\) to Cu, so Fe is the reducing agent.
✅ Answer: (C)
A substance that is oxidised (loses electrons) is the reducing agent, since it causes another species to be reduced.
Here, Fe reduces \(Cu^{2+}\) to Cu, so Fe is the reducing agent.
✅ Answer: (C)
▶️ Answer/Explanation
An oxidising agent is a species that is itself reduced while causing another species to be oxidised.
In \(Zn^{2+} + Mg \rightarrow Zn + Mg^{2+}\), the zinc ion gains electrons to become zinc metal — it is reduced — while magnesium is oxidised.
In all the other equations, zinc itself loses electrons (is oxidised), meaning it acts as the reducing agent, not the oxidising agent.
✅ Answer: (C)
In \(Zn^{2+} + Mg \rightarrow Zn + Mg^{2+}\), the zinc ion gains electrons to become zinc metal — it is reduced — while magnesium is oxidised.
In all the other equations, zinc itself loses electrons (is oxidised), meaning it acts as the reducing agent, not the oxidising agent.
✅ Answer: (C)
▶️ Answer/Explanation
Aluminium atoms lose electrons (are oxidised) to form \(\text{Al}^{3+}\) ions, so statement 4 is correct.
Iron(III) ions, \(\text{Fe}^{3+}\), gain electrons to become neutral iron atoms, meaning they are reduced, so statement 1 is correct.
Oxide ions, \(\text{O}^{2-}\), lose electrons to become oxygen atoms bound in \(\text{Al}_2\text{O}_3\) rather than gaining electrons, and since \(\text{Fe}_2\text{O}_3\) is itself reduced, it acts as the oxidising agent, not the reducing agent — so statements 2 and 3 are both incorrect.
✅ Answer: (B)
Iron(III) ions, \(\text{Fe}^{3+}\), gain electrons to become neutral iron atoms, meaning they are reduced, so statement 1 is correct.
Oxide ions, \(\text{O}^{2-}\), lose electrons to become oxygen atoms bound in \(\text{Al}_2\text{O}_3\) rather than gaining electrons, and since \(\text{Fe}_2\text{O}_3\) is itself reduced, it acts as the oxidising agent, not the reducing agent — so statements 2 and 3 are both incorrect.
✅ Answer: (B)