Question

rank HF, HCl and HI in order of decreasing pka and explain your reasoning.

Answer 1

pKa values order :   HI < HCl < HF

explanation:

pKa value increases acidity decreases. lesser pKa value indicate strong acid

F, Cl , I are same group elements . the acidity order of hydrides increases it is due to increase in size of halogen atom .

if halogen atom size increases the bond length between halogen and hydrogen increases so that the bond dissociation energy is decreases . so HI bond wil be broken easily than HF bond. that means HI can readily loose H+ ion . so it is strong acid .