Which one of the following reactions does not occur during extraction of copper?

For a reversible reaction $A \rightleftharpoons B$, the $\Delta H _{\text {forward }}$ reaction $=20\,kJ\,mol ^{-1}$. The activation energy of the uncatalysed forward reaction is $300\,kJ\,mol ^{-1}$. When the reaction is catalysed keeping the reactant concentration same, the rate of the catalysed forward reaction at $27^{\circ}\,C$ is found to be same as that of the uncatalysed reaction at $327^{\circ}\,C$. The activation energy of the cataysed backward reactoion is $….\,kJ\,mol { }^{-1}$.

The byproduct in the extraction of iron is

$AgCl$ on fusion with sodium carbonate, gives

Select the correct statement :