Question

$△Hand△S$ for the reaction,
$A{g}_{2}O\left(s\right)\to 2Ag\left(s\right)+\frac{1}{2}{O}_2\left(g\right)$
are $30.56kJmo{l}^{-1}$ and $66.0Jmo{l}^{-1}{K}^{-1}$ respectively. Calculate the temperature at which free energy change for the reaction will be zero. Predict whether the reaction will be sponteneous above or below this temperature (in K)

• A. $563K$, reaction will be sponteneous above this temperature.
• B. $463K$, reaction will be sponteneous above this temperature.
• C. $563K$, reaction will be sponteneous below this temperature.
• D. $463K$, reaction will be sponteneous below this temperature.

Answer 1

The correct option is B $463K$, reaction will be sponteneous above this temperature.

We know that,
$△G=△H-T△S$
At equilibrium, $△G=0$
so that $0=△H-T△S$
or $T=\frac{△H}{△S}$
Given that, $△H=30.56kJmo{l}^{-1}$
$=30560Jmo{l}^{-1}$
$△S=66.0J{K}^{-1}mo{l}^{-1}$
$T=\frac{30560}{66}=463K$
Above this temperature, $△G$ will be negative and the reaction will be spontaneous.