Question

The acidity (acid strength) of halo acids increases in the order:

• A. $HCl<HF<HBr<HI$
• B. $HF<HCl<HBr<HI$
• C. $HF<HCl<HI<HBr$
• D. $HF<HBr<HCl<HI$

Answer 1

The correct option is B $HF<HCl<HBr<HI$

$HF$ displays hydrogen bonding and also the bond strength is the greatest in $HF$. The bond dissociation energy decreases in the order $H-F>H-Cl>H-Br>H-I$. Further, the decrease in electronegativity and increase in atomic size increases the acidity of halogen hydrides.
Therefore the order of acidity is $HF<HCl<HBr<HI$.