Thermite is a mixture of aluminium powder and ferric oxide. When this mixture is ignited, $$Al$$  reduces $$F{e_2}{O_3}$$  to $$Fe$$  while itself gets oxidized to $$A{l_2}{O_3}.$$

\[\begin{align} & \left( \text{i} \right)\underset{\text{(impure)}}{\mathop{Ni}}\,+4CO\xrightarrow{{{50}^{\circ }}C}\left[ \underset{\text{(volite)}}{\mathop{Ni{{\left( CO \right)}_{4}}}}\, \right]\xrightarrow{{{230}^{\circ }}C}\underset{\text{(pure)}}{\mathop{Ni}}\,+4CO\uparrow \\ & \left( \text{ii} \right)C{{u}_{2}}S+\frac{3}{2}{{O}_{2}}\xrightarrow{\Delta }C{{u}_{2}}O+S{{O}_{2}} \\ & C{{u}_{2}}S+2C{{u}_{2}}O\xrightarrow[\text{temp}\text{.}]{\text{high}}6Cu+S{{O}_{2}} \\ & \left( \text{iii} \right)MgC{{l}_{2}}\left( s \right)\xrightarrow{\text{electrolysis}}M{{g}^{2+}}\left( l \right)+2C{{l}^{-}}\left( l \right) \\ & \text{At cathode :} \\ & M{{g}^{2+}}2{{e}^{-}}\to Mg\left( s \right) \\ & \text{At anode :} \\ & 2C{{l}^{-}}\left( l \right)\to C{{l}_{2}}\left( g \right)+2{{e}^{-}} \\ \end{align}\]

The standard free energies of formation $$\left( {\Delta G_f^ \circ } \right)$$  of most of the sulphides are more negative than those of $$C{S_2}$$  and $${H_2}S.$$  Hence, neither carbon nor hydrogen can reduce metal sulphides to metal. The standard free energies of formation of oxides are much lower than those of $$S{O_2}.$$  Therefore, oxidation of metal sulphides to metal oxides is thermodynamically favourable. Hence sulphide ore is roasted to the oxide before reduction.

Pure metal always deposits at cathode.

It is an example of auto-reduction in which unoxidised copper sulphide reduces copper oxide.

In the extraction of aluminium by Hall- Heroult process purified $$A{l_2}{O_3}$$  is mixed with $$Ca{F_2}$$  to lower the melting point by $$A{l_2}{O_3}$$  and increase the conductivity of molten mixture.

Zincite is $$ZnO.$$

Magnetite $$ - F{e_3}{O_4}$$
Malachite $$ - CuC{O_3} \cdot Cu{\left( {OH} \right)_2}$$
Cassiterite $$ - Sn{O_2}.$$
Pyrolusite $$ - Mn{O_2}$$

In the extraction of copper from its sulphide ore, when ore is subjected to roasting, some of it is oxidised to $$C{u_2}O$$   which reacts with the remaining $${C{u_2}S}$$   ( sulphide ore ) to give copper metal.
$$2C{u_2}S + 3{O_2} \to 2C{u_2}O + 2S{O_2} \uparrow $$
$$2C{u_2}O + C{u_2}S \to 6Cu + S{O_2} \uparrow $$
In this process $$C{u_2}S$$   behaves as reducing agent.

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