WAEC Chemistry 2023 Paper

Concept:Compounds in the same homologous series have the same general formula and differ by a $-\mathrm{CH}_2-$ unit.Explanation:Alkanes follow the general formula $\mathrm{C}_n\mathrm{H}_{2n+2}$.For $\mathrm{C}_2\mathrm{H}_6$: $n=2$, so $\mathrm{C}_2\mathrm{H}_{2(2)+2}=\mathrm{C}_2\mathrm{H}_6$.For $\mathrm{C}_4\mathrm{H}_{10}$: $n=4$, so $\mathrm{C}_4\mathrm{H}_{2(4)+2}=\mathrm{C}_4\mathrm{H}_{10}$.Both satisfy the alkane general formula and are saturated hydrocarbons.Therefore, they belong to the same homologous series.The other options mix alkanes with alkenes, which have different general formulas.Answer:A. $\mathrm{C}_2\mathrm{H}_6$ and $\mathrm{C}_4\mathrm{H}_{10}$