The correct order of the thermal stability of hydrogen halides (H-X) is
HI > HBr > HCl > HF
HF > HCl > HBr > HI
HCl < HF > HBr < HI
HI > HCl < HF < HBr
The order of thermal stability of hydrogen halides is, HF > HCl > HBr > HI, due to decrease of bond energy from HF toHI