WAEC Chemistry 2020 Paper

Concept:A metal can displace hydrogen from water only if it is above hydrogen in the reactivity series.Explanation:Sodium $\mathrm{(Na)}$ and potassium $\mathrm{(K)}$ are alkali metals placed much above hydrogen in the reactivity series.They react vigorously with cold water to release hydrogen gas:$$2\mathrm{Na} + 2\mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{NaOH} + \mathrm{H}_2 \uparrow$$$$2\mathrm{K} + 2\mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{KOH} + \mathrm{H}_2 \uparrow$$Zinc reacts with steam to form zinc oxide and hydrogen gas:$$\mathrm{Zn} + \mathrm{H}_2\mathrm{O}\,(\mathrm{steam}) \rightarrow \mathrm{ZnO} + \mathrm{H}_2 \uparrow$$Copper lies below hydrogen in the reactivity series, so it cannot displace hydrogen from water.Therefore, copper does not react with water to produce hydrogen gas.Answer:A. Copper