KCET 2026 Chemistry Solved Paper

Concept:Hybridisation of carbon and resonance effects determine the nature of the carbon-chlorine bond.Explanation:In methyl chloride, $\mathrm{CH}_3\mathrm{Cl}$, the carbon is $sp^3$ hybridised.Hence, the $\mathrm{C}-\mathrm{Cl}$ bond is a normal single bond.In chlorobenzene, $\mathrm{C}_6\mathrm{H}_5\mathrm{Cl}$, the chlorine atom is attached to an $sp^2$ hybridised carbon of the benzene ring.The lone pair on chlorine participates in resonance with the benzene ring, giving the $\mathrm{C}-\mathrm{Cl}$ bond some partial double bond character.A bond with partial double bond character is shorter and stronger than a pure single bond.Therefore, the $\mathrm{C}-\mathrm{Cl}$ bond in chlorobenzene is shorter and stronger than that in methyl chloride.So, the $\mathrm{C}-\mathrm{Cl}$ bond in methyl chloride is longer and weaker.Answer:$\mathrm{C}-\mathrm{Cl}$ bond in methyl chloride is longer and weaker.Correct option: D.