UPSC NDA 2 2022 General Ability Solved Paper

Concept:The molecular formula $\mathrm{C}_4\mathrm{H}_8$ matches the general formula of alkenes, which are unsaturated hydrocarbons with one carbon-carbon double bond.Explanation:Alkenes have the general formula $\mathrm{C}_n\mathrm{H}_{2n}$.For $n = 4$, the formula becomes $\mathrm{C}_4\mathrm{H}_8$.Hence, $\mathrm{C}_4\mathrm{H}_8$ belongs to the homologous series of alkenes.Cycloalkanes (such as cyclobutane) also have the formula $\mathrm{C}_n\mathrm{H}_{2n}$, so $\mathrm{C}_4\mathrm{H}_8$ can represent a cycloalkane as well.However, the given option D is cycloalkenes, which have the general formula $\mathrm{C}_n\mathrm{H}_{2n-2}$ and do not fit $\mathrm{C}_4\mathrm{H}_8$.Therefore, among the provided options, only alkenes are correct.Alkanes have formula $\mathrm{C}_n\mathrm{H}_{2n+2}$ and alkynes have $\mathrm{C}_n\mathrm{H}_{2n-2}$, neither matching $\mathrm{C}_4\mathrm{H}_8$.Answer:B. alkenes