Question

The correct order of the thermal stability of hydrogen halides $(H-X)$ is

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

Answer 1

Answer: (C)

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