Which gas is a mixture of carbon monoxide $(CO)$ and dihydrogen $(H_2)$?

Which non-metal element exists in a liquid state at room temperature?

Which metal can be beaten into very thin foils?

Which alloy is used to make surgical instruments?

Compound $X$ and aluminium are used to join railway tracks.
$(a)$ Identify the compound $X$.
$(b)$ Name the reaction.
$(c)$ Write down its chemical reaction.

Write the balanced chemical equation for each of the following cases:
$(a)$ Magnesium is treated with very dilute $HNO_3$.
$(b)$ Aluminium powder is added to $Fe_2O_3$.
$(c)$ Zinc sulphide is roasted.