WAEC Chemistry 2024 Paper

Concept:A redox reaction involves simultaneous oxidation and reduction, identified by changes in oxidation numbers.Explanation:In the reaction: $\mathrm{Ni^{2+}(aq) + Fe(s) \rightarrow Ni(s) + Fe^{2+}(aq)}$, assign oxidation numbers.Nickel changes from $\mathrm{Ni^{2+}}$ with oxidation number $+2$ to $\mathrm{Ni}$ metal with oxidation number $0$.This is a decrease in oxidation number, so $\mathrm{Ni^{2+}}$ is reduced.Iron changes from $\mathrm{Fe}$ metal with oxidation number $0$ to $\mathrm{Fe^{2+}}$ with oxidation number $+2$.This is an increase in oxidation number, so Fe is oxidized.The substance that is reduced acts as the oxidizing agent, so $\mathrm{Ni^{2+}}$ is the oxidizing agent.The substance that is oxidized acts as the reducing agent, so Fe is the reducing agent.Therefore, $\mathrm{Ni^{2+}}$ ions are reduced and Fe acts as the reducing agent.Answer:Option D: $\mathrm{Ni^{2+}}$ ions are reduced and Fe acts as a reducing agent.