JAMB Chemistry 2015 Paper

Concept:Isomers are different compounds that share the same molecular formula but have different structural arrangements of atoms.Explanation:The molecular formula $\mathrm{C}_6\mathrm{H}_{14}$ matches the general alkane formula $\mathrm{C}_n\mathrm{H}_{2n+2}$. When $n = 6$, six carbon atoms can be arranged into five distinct structural isomers.The straight-chain isomer is $n$-hexane.Moving one carbon atom into a branch on a five-carbon chain gives two isomers: $\text{2-methylpentane}$ and $\text{3-methylpentane}$.Placing two methyl branches on a four-carbon chain gives two more isomers: $\text{2,2-dimethylbutane}$ and $\text{2,3-dimethylbutane}$.No further distinct arrangements are possible without duplicating these structures.Therefore, the total number of isomers of $\mathrm{C}_6\mathrm{H}_{14}$ is five.Answer:B. $5$