Explain the following :
HF is a weaker acid than HI.

Explanation

It is mainly due to following two reasons.
(a) HF molecules are hydrogen bonded as shown below.
`-overset(delta+)H-overset(delta-)F-overset(delta+)H-overset(delta-)F-overset(delta+)H-overset(delta-)F-overset(delta+)H-overset(delta-)F`
As a result the H atoms get trapped between two F atoms. Therefore release of proton from H-F is more difficult than in HI in which hydrogen bond is not present.
(b) Bond dissociation energy of HI is less than HF. As such, HI can easily give `H^+` in aqueous solutions and is a stronger acid than HF.