Which statement is incorrect regarding the Hall-Heroult process for the metallurgy of aluminium?
$1$. Use of $Na_3AlF_6$ lowers the melting point of $Al_2O_3$.
$2$. Steel vessel with a lining of carbon acts as the cathode.
$3$. Graphite is used as the anode.
$4$. Carbon dioxide gas is generated at the cathode.

Heating a mixture of $Cu_2O$ and $Cu_2S$ will give

How is copper extracted from low grade copper ores?

What is obtained when a mixture of $Cu_2O$ and $Cu_2S$ is heated?

The Ellingham diagram for zinc,magnesium,and carbon converting into corresponding oxides is shown below. To make the following reduction process spontaneous,the temperature should be:
$ZnO + C \to Zn + CO$

Observe the following statements:
Statement-$I$: The choice of reducing agent for the reduction of an oxide ore can be predicted by using Ellingham diagram,a plot of $\Delta G^{\ominus}$ vs $T$.
Statement-$II$: According to Ellingham diagram,metal oxide with higher $\Delta G^{\ominus}$ is more stable than the oxide with lower $\Delta G^{\ominus}$.