Which of the following elements is present as the impurity to the maximum extent in the pig iron?

Calcium is extracted by the electrolysis of

Suggest a condition under which magnesium could reduce alumina. The two equations are:
$(a)$ $\frac{4}{3} Al + O_2 \rightarrow \frac{2}{3} Al_2O_3$
$(b)$ $2 Mg + O_2 \rightarrow 2 MgO$

In the alumino-thermite process,$Al$ acts as:

Heating with carbon in absence of air is known as:

The cyanide process is used for the extraction of which of the following?