A process has H = 200\,J mol-1 and S = 40\,JK-1mol-1. Out of the values given below, choose the minimum temperature…

🧠 Spontaneity requires $\Delta G = \Delta H - T\Delta S < 0$: threshold at $T = \Delta H / \Delta S$ The process becomes spontaneous when $T > \Delta H / \Delta S$ (for positive $\Delta H$ and positive $\Delta S$).

🗺️ Calculation $T_{\text{min}} = \frac{\Delta H}{\Delta S} = \frac{200\text{ J mol}^{-1}}{40\text{ J K}^{-1}\text{mol}^{-1}} = 5\text{ K}$

The reaction becomes spontaneous above 5 K. The minimum temperature from the options above which spontaneity holds is (a) 20 K — at any temperature above 5 K, the process is spontaneous.

⚠️ Trap: The formula $T = \Delta H / \Delta S$ gives the exact threshold. Any temperature listed in the options that is above this threshold will make the process spontaneous.

$\boxed{\text{Answer: (a)}}$