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

What happens when
$(a)$ $ZnCO_{3}$ is heated in the absence of oxygen?
$(b)$ $A$ mixture of $Cu_{2}O$ and $Cu_{2}S$ is heated?

Why do ionic compounds have high melting points? State the reason.

Which metal oxide dissolves in water to form an alkali?

Which metal is the second most abundant metal found on Earth?

$(a)$ 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.