Q. The $\mathrm{\Delta}H_{f}^{o}$ of $O_{3},\ CO_{2},\ NH_{3}$ and HI are 142.2 $- 393.3,\ - 46.2$ and $+ 25.9$ kJ per mol respectively. The order of their increasing stabilities will be
A) $O_{3},CO_{2},NH_{3},\ HI$
B) $CO_{2},NH_{3},HI,O_{3}$
C) $O_{3},HI,NH_{3},CO_{2}$
D) $NH_{3},HI,CO_{2},O_{3}$
Explanation
(c)
Energy absorbed $\propto \frac{1}{stability\ of\ compound}$
Energy released $\propto$ stability of compound
Thus, the order of stability is
$142.2 > 25.9 > - 46.2 > - 393.2$
$ie,\ O_{3} > HI > NH_{3} > CO_{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.