$(H F $ to $HI $ $ ( HF > HCl > HBr > HI )$
Due to successive decrease in the strength of $H X$ bonds, bonds dissociation enthalpy decreases from $H F$ to $H I$ $H X$ Bond dissociation $\underset{574.0}{H F}>\underset{428.1}{H C l}>\underset{362.5}{H B r}>\underset{294}{H I}$ enthalpy ( $k J / m o l)$