VITEEE 2018 Paper

The H-X bond strength decreases from HF to HI. i.e. HF > HCl > HBr > HI. Thus HF is most stable while HI is least stable. The decreasing stability of the hydrogen halide is also reflected in the values of dissociation energy of the H-X bond
H - F : 135 kcal mol−1
H - Cl : 103 kcal mol−1
H - Br : 87 kcal mol−1
H - I : 71 kcal mol−1