JAMB Chemistry 2024 Paper

Concept:The difference in molecular mass between an alkene and an alkyne with the same number of carbon atoms comes from their hydrogen atoms.Explanation:The general formula for an alkene is $\mathrm{C}_n\mathrm{H}_{2n}$.For an alkene with 6 carbon atoms, $n = 6$, so the formula is $\mathrm{C}_6\mathrm{H}_{12}$.The general formula for an alkyne is $\mathrm{C}_n\mathrm{H}_{2n-2}$.For an alkyne with 6 carbon atoms, the formula is $\mathrm{C}_6\mathrm{H}_{10}$.Since both molecules have 6 carbon atoms, the only difference is $2$ fewer hydrogen atoms in the alkyne.The difference in molecular mass is the mass of $\mathrm{H}_2$: $2 \times 1 = 2$.So, the difference in molecular mass is $2$.Answer:The correct answer is Option C: $2$.