Question

Which of the following is thermally more stable?

• A. $HI$
• B. $HBr$
• C. $HCl$
• D. $HF$

Answer 1

The correct option is D $HF$

Thermal stability of hydrides $\propto \frac{1}{\text{molecular mass}}\propto$ difference in electronegativity.

$H-F$ bond is very strong as compared to other halogen - hydrogen bonds due to large electronegativity difference between $H$ and $F$.

$\therefore$ The thermal stability of $HF$ is more than other hydrides.