Question
Question: The correct order of the thermal stability of hydrogen halides (H – X) is :...
The correct order of the thermal stability of hydrogen halides (H – X) is :
A
HI > HBr > HCl > HF
B
HF > HCl > HBr > HI
C
HCl < HF < HBr < HI
D
HI > HCl < HF < HBr
Answer
HF > HCl > HBr > HI
Explanation
Solution
As the size of the halogen atom increases from F to I, H–X bond length in HX molecules also increases from H–F to H–I (H–F < H–CI < H–Br < H–I). The increase in H–X bond length decreases the strength of H–X bond from H–F to H–I. The decrease in the strength of H–X bond is evident from the fact that H–X bond dissociation energies decrease from H–F to H–I . Due to successive decrease in the strength of H–X bond from H–F to H–I, thermal stability of HX molecules also decreases from HF to HI (HF > HCI > HBr > HI).