why is HI more acidic than HCL

                 As we all know, the easier it is to release a proton in an aqueous solution, the stronger is the acid. In the case of the bond strength between HI and HCl, due to the larger size of iodine than chlorine, the H-I bond is weaker , whereas the H-Cl bond is stronger due to the better overlap of the sigma bonds which is not found in the case of H-I. So it is clear that H-Cl bond is stronger and it is a weaker acid as it is difficult to break the H-Cl bond. Moreover, it would be easier to release a Hydrogen ion from HI than from HCl and hence, HI more acidic than HCl.