Question
Determine whether the following reaction will be spontaneous or non-spontaneous under standard conditions.
$Zn _{(s)}+ Cu ^{2+} \rightarrow Zn ^{2+}+ Cu _{( ss } \Delta H ^0=-219 kJ , \Delta S ^0=-21 JK ^{-1}$

Answer

$\begin{aligned}
& \text { Given : } \Delta H^0=-219 kJ \\
& \Delta S^0=-21 JK ^{-1}=0.021 kJ K ^{-1} \\
& \Delta G^0=?
\end{aligned}$
For standard conditions : Pressure $=1 atm$
$\begin{aligned}
& \text { Temperature }=T=298 K \\
& \Delta G^0=\Delta H^0-T \Delta S^0 \\
& =-219-298 \times(-0.021) \\
& =-219+6.258 \\
& =-212.742 kJ
\end{aligned}$
Since $\Delta G<0$, the reaction is spontaneous.
The reaction is spontaneous.

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