Out of `C_(6)H_(5)CH_(2)Cl` and `C_(6)H_(5)CHClC_(6)H_(5)`, which is more easily hydrolysed by aqueous KOH.

Explanation

`C_(6)H_(5)CH_(2)Cl` is a `1^(@)` aralkyl halide while `C_(6)H_(5)CH(Cl)C_(6)H_(5)` is a `2^(@)` aralkyl halide.

In `S_(N)1` reactions, the reactivity depends upon the stability of carbocations, since the carbocation `C_(6)H_(5)overset(+)(C)HC_(6)H_(5)` (where the +ve charge is delocalised over the `C_(6)H_(5)` rings) derived from `C_(6)H_(5)-CHCl-C_(6)H_(5)` is more stable than the carbocation, `C_(6)H_(5)CHClC_(6)H_(5)` gets hydrolysed more easily than `C_(6)H_(5)` ring) derived from `C_(6)H_(5)CH_(2)Cl`, therefore, `C_(6)H_(5)CHClC_(6)H_(5)` gets hydrolysed more easily than `C_(6)H_(5)CH_(2)Cl` under `S_(N)2` conditions.
However, under `S_(N)2` conditions, the reactivity depends on steric hindrance, therefore, under `S_(N)2` conditions, `C_(6)H_(5)CH_(2)Cl` (with lesser steric hindrance) gets hydrlysed more easily than `C_(6)H_(5)CHClC_(6)H_(5)`.