Question

What is the order of reactivity of halogen acids towards alcohol and why is it so?

Answer 1

As we know that atomic size increases from F to I, so bond length of H-X bond also gets increased and so bond dissociation energy decreases. Hence, ionisation of H-X increases, therefore acidic strength increases in the order

HF < HCl < HBr < HI

So, the reactivity of alcohols towards haloacids is in the order - HI>HBr>HCl