See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Concept: The SN2 reaction is a bimolecular nucleophilic substitution reaction. Its rate law is second-order overall: rate = k[nucleophile][electrophile]. This means the rate depends on the concentration of BOTH the nucleophile and the electrophile, each to the first power. Reasoning: If the concentration of the electrophile is increased by a factor of 3, the rate increases by a factor of 3 (since rate is first-order in electrophile). Simultaneously, if the concentration of the nucleophile is increased by a factor of 3, the rate increases by another factor of 3 (since rate is first-order in nucleophile). Combined effect: new rate = k × (3[nucleophile]) × (3[electrophile]) = 9 × k[nucleophile][electrophile] = 9 × original rate. So the rate increases by a factor of 9. Why other options fail: (a) A factor of 6 would result from adding the two factors (3 + 3), which is incorrect; rate factors multiply, not add. (c) A factor of 3 decrease has no basis in the SN2 rate law. (d) Remaining the same would only occur if neither concentration changed or if the reaction were zero-order, which SN2 is not. Therefore, the correct answer is B.