JAMB Chemistry 2023 Paper

Concept:A straight-chain alkane has all its carbon atoms joined in one continuous, unbranched chain.Explanation:Straight-chain alkanes fit the general formula $\mathrm{C}_n\mathrm{H}_{2n+2}$ and contain no side branches. Cyclopentane, $\mathrm{C}_5\mathrm{H}_{10}$, is a cycloalkane because its carbons form a ring, not a straight chain. Isobutane and 2-methylpropane are the same branched compound, $\mathrm{C}_4\mathrm{H}_{10}$. Pentane, $\mathrm{C}_5\mathrm{H}_{12}$, has all five carbon atoms linked end to end without any branch. Hence, pentane is the only straight-chain alkane listed.Answer:D. Pentane ($\mathrm{C}_5\mathrm{H}_{12}$)