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

The correct option is C $HF>HCl>HBr>HI$

The $H-F$ bond length is smallest and hence, the bond energy is highest. Thus, it is highly stable.

However, $HI$ bond length is longest and this, its bond energy is least. The $HI$ bond can thus be easily broken.

Therefore, the order is $HF>HCl>HBr>HI$.