Question

a) For the reaction : $2A\left(g\right)+B\left(g\right)⟶2D\left(g\right)$, $\Delta U=-10.5kJ$ and $\Delta S=-44.1{kJ}^{-1}$. Calculate $\Delta G$ for the reaction, and predict whether the reaction may occur spontaneously.
b) Predict whether the reaction is spontaneous or not at high temperature.

Answer 1

Given that $2A+B⟶2D_{\left(g\right)}$ $\Delta U=-10.5kJ$

$\Delta ng=np-nr$

$=2-(2+1)=-1$

$\Delta H=\Delta U^o+\Delta ngRT$

$=-10.5+(-1)0.008314\times 298=-12.947kJ$

$\Delta G=\Delta H-J\Delta S$

$=-12.947-298\times (-44\times {10}^{-3})=0.165kJ$

$\Delta G$ is positive, then the reaction won't occur spontaneously.