Question

HF, HCl, HBr, HI (thermal stability)

Hint:

Thermal stability of hydrogen halides decreases as bond strength weakens down the group.

Answer 1

Increasing Order of Thermal Stability: Thermal stability of hydrogen halides (HX) decreases down the group due to decreasing bond strength 
(H-F) being the strongest and (H-I) the weakest. \[ HI < HBr < HCl < HF \]