Metal $X$ obtained from sphalerite ore can be purified by which of the following methods?

Outline the principles of refining of metals by the following methods:
$(i)$ Zone refining
$(ii)$ Electrolytic refining
$(iii)$ Vapour phase refining

Blister copper is

Which one of the following methods can be used to obtain highly pure metal which is liquid at room temperature?

Explain the electrolytic refining of metals.

Blister copper is refined by stirring molten impure metal with green logs of wood because such wood liberates hydrocarbon gases (like $CH_4$). This process $X$ is called . . . . . . . . . and the metal contains impurities of $Y$ is . . . . . . . . .