WAEC Chemistry 2025 Paper

Concept:$\mathrm{Na}^+$ and $\mathrm{K}^+$ are cations that can gain one electron during reduction.Explanation:Both ions have already lost their valence electron, so they do not tend to give electrons.Instead, they accept one electron to form neutral atoms:$$\mathrm{Na}^+ + e^- \rightarrow \mathrm{Na}$$$$\mathrm{K}^+ + e^- \rightarrow \mathrm{K}$$Their standard reduction potentials are negative:$$E^\circ_{\mathrm{Na}^+/\mathrm{Na}} = -2.71\,\mathrm{V}$$$$E^\circ_{\mathrm{K}^+/\mathrm{K}} = -2.93\,\mathrm{V}$$Therefore, they do not have positive reduction potential.Also, since oxidation potential is the reverse of reduction potential, these ions do not have negative oxidation potential.So the common property is their tendency to accept electrons.Answer:C. tendency to accept electrons