What are the substances added to a catalyst to increase its efficiency called?

What is an alloy called if one of the metals is $Mercury$?

Which method/process is used to obtain aluminium from pure alumina?

What is used as a catalyst in the production of sulfuric acid by the contact process?

Malachite is an ore of which metal?

$(a)$ Consider the following chemical equation:
$Fe_{2}O_{3} + 2Al \rightarrow Al_{2}O_{3} + 2Fe$
Name two categories in which you can place this reaction.
$(b)$ Define the term 'Oxidation' of a substance and name the substance oxidised and the oxidising agent in the above reaction.