What is Thomas slag?

The modern method for the manufacture of steel is:

In the process of extraction of gold,roasted gold ore reacts as follows. Identify the complexes $[X]$ and $[Y]$:
$\text{Roasted gold ore} + CN^{-} + H_2O \xrightarrow{O_2} [X] + OH^{-}$
$[X] + Zn \to [Y] + Au$

Although carbon and hydrogen are better reducing agents,they are not used to reduce metallic oxides at high temperatures. Why?

In the electrolysis of aluminium oxide,which of the following is added to accelerate the process?

Aluminum is obtained from alumina $(Al_2O_3)$ by the electrolysis of a molten mixture of: