Question

Arrange halogen acids in the decreasing order of thermal stability.

Answer 1

1. The order of thermal stability of halogen acids is HF > HCl > HBr > HI.
2. HF is the most thermally stable due to the strongest \[\ce{H - F}\] bond.
3. Thermal stability decreases down the group because the bond strength of \[\ce{H - X}\] decreases.
4. HI is least stable, as the \[\ce{H - I}\] bond is the weakest.

This order follows the decreasing bond dissociation energy from HF to HI.