Why is the reactivity of all the three classes of alcohols with conc. HCl and `ZnCl_(2)` (Lucas reagent) different ?

Explanation

The reaction of alcohols with conc. HCl and `ZnCl_(2)` (Lucas reagent) occurs through intermediate formation of carbocations. Obviously, more stable the carbocation, more reactive is the alcohol. Since the stability of carbocations follows the order: `3^(@) gt 2^(@) gt 1^(@)`, thereore, reactivity of alcohols towards Lucas reagents follows the same order, i.e., `3^(@) gt 2^(@) gt 1^(@)`.