CBSE Class 10 Science 2017 · Paper 31(B)/C · Question 7

B (${\text{C}}_3{\text{H}}_6$) is more likely to show an addition reaction. It fits the general formula ${\text{C}}_n{\text{H}}_{2n}$ of the alkenes; taken as the open-chain compound the question intends, it is propene, an unsaturated hydrocarbon with a carbon–carbon double bond, across which hydrogen can add. A (${\text{C}}_4{\text{H}}_{10}$) fits ${\text{C}}_n{\text{H}}_{2n+2}$: it is a saturated alkane with only single bonds, and it shows substitution, not addition. Equation: ${\text{CH}}_3-\text{CH}={\text{CH}}_2+{\text{H}}_2\stackrel{\text{Ni}}{\to }{\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_3$ (propene to propane). Use: this addition of hydrogen (hydrogenation) is used to convert vegetable oils into vegetable ghee, with a nickel catalyst.