Solution

(a) Hydrogen gas combines with nitrogen to form ammonia.

$$H_2(g) + N_2(g) \rightarrow NH_3$$

The balanced equation for this reaction can be written as:

$$3H_2(g) + N_2(g) \rightarrow 2NH_3$$


(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

$$H_2S(g) + O_2(g) \rightarrow H_2O + SO_2$$

The balanced equation for this reaction can be written as:

$$2H_2S(g) + 3O_2(g) \rightarrow 2H_2O + 2SO_2$$


(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

$$BaCl_2 + Al_2(SO_4)_3 \rightarrow AlCl_3 + BaSO_4\downarrow$$

The balanced equation for this reaction can be written as:

$$3BaCl_2 + Al_2(SO_4)_3 \rightarrow 2AlCl_3 + 3BaSO_4\downarrow$$


(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

$$K + H_2O \rightarrow KOH + H_2$$

The balanced equation for this reaction can be written as:

$$2K + 2H_2O \rightarrow 2KOH + H_2$$