Question

$P\left(g\right)+2Q\left(g\right)\to P{Q}_2\left(g\right);\Delta H=18kJmo{l}^{-1}$
The entropy change of the above reaction $\left(\Delta S_{system}\right)is60J{K}^{-1}mo{l}^{-1}$ At what temperature, the reaction becomes spontaneous?

• A. Below $200K$
• B. Above $300K$
• C. Below $300K$
• D. Above $200K$ and below $300K$

Answer 1

The correct option is B Above $300K$

For spontaneous process, $\Delta G<0$
$\therefore \Delta H-T\Delta S<0,\Delta H<T\Delta S\therefore T>\frac{\Delta H}{\Delta S}=\frac{18000}{60}=300K$