• # question_answer 30) For the reaction at 298 K : $2A+B\to C$ $\Delta H=400kJ\,mo{{l}^{-1}},\Delta S=2kJ\,\,{{K}^{-1}}mo{{l}^{-1}}$ At what temperature will the reaction become spontaneous considering $\Delta H$ and $\Delta S$ to be constant over the temperature range?

Information shadow: $\Delta H=400\times {{10}^{3}}J\,mo{{l}^{-1}}$ $\Delta S=2000J{{K}^{-1}}mo{{l}^{-1}}$ Problem solving strategy: A reaction is spontaneous, when $\Delta G=-ve$ $\therefore$ $(\Delta H-T\Delta S)\frac{\Delta H}{\Delta S}$ Working it out: $T>\frac{400\times 1000}{2000}$ $T>200K$ Reaction will be spontaneous above 200 K.