The formula of carnallite is:

In the extraction of aluminium:

Process $\mathrm{X}$: employed for red bauxite to remove iron oxide (main impurity).

Process $\mathrm{Y}$ (Serpeck's process): used for white bauxite to remove $\mathrm{Z}$ (main impurity) then,

select the correct option for the process $\mathrm{X}$ and impurity $\mathrm{Z}$.

Which of the following metals may be present in the anode mud during electro-refining of copper?

$\mathrm{I}$. Gold

$\mathrm{II}$. Iron

$\mathrm{III}$. Silver

$\mathrm{IV}$. Magnesium