The mixture obtained from the roasting of copper pyrites is ......... .

Consider the following statements:
Roasting is carried out to:
$(i)$ convert sulphide to oxide and sulphate
$(ii)$ remove water of hydration
$(iii)$ melt the ore
$(iv)$ remove arsenic and sulphur impurities
Of these statements:

In metallurgy,calcination is used for ...... .

Which of the following reactions is an example of the calcination process?

The pair that does $Not$ require calcination is

$A$ reverberatory furnace is employed in the metallurgical process mainly for