Question

Although the dissolution of ammonium chloride $\left({NH}_{4}Cl\right)$ in water is an endothermic reaction, even then it is spontaneous because:

• A. $\Delta S=-ve$
• B. $\Delta S=0$
• C. $T\Delta S<\Delta H$
• D. $\Delta S=-ve$ and $T\Delta S<\Delta H$

Answer 1

Answer: (D)

$\Delta S=-ve$ and $T\Delta S<\Delta H$

Gibb's free energy equation : $\Delta G=\Delta H-T\Delta S$

For spontaneous process : $\Delta G<0$

For endothermic reaction : $\Delta H>0$

The term $T\Delta S$ is positive & is less than $\Delta H$ for dissolution of ${NH}_{4}Cl$ in water.

$\therefore \Delta H>0\&T\Delta S<\Delta H$

$\therefore \Delta G<0$

$\therefore$ The reaction is spontaneous.