R-Cl is hydrolysed to R-OH slowly but the reaction is rapid in presence of KI as catalyst. Explain.

Explanation

KI supplies `l^(-)` ion which is strong nucleophile and hence reacts rapidly with R-Cl to form `R-I. I^(-)` is also a better leaving group than `Cl^(-)` . Hence R-I is hydrolysed rapidly to form R-OH and `I^(-).. I^(-)`  ion is again used in converting R-Cl to R-I.
`R-Cl + H_2O overset("slow)(rarr)R-OH+Cl^(-)`
`R-Cl + I^(-) underset(-Cl^(-))overset("fast")(rarr) R - I underset("fast")overset(+H_2O)(rarr)R-OH`