[" Translate the following statements into chemical equations and then balance them."],[" (a) Hydrogen gas combines with nitrogen to form ammonia."],[" (b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide."],[" (c) Barium chloride reacts with aluminium sulphate to give alumininm chloride "],[" and a precipitate of barium sulphate."],[" (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen "],[" gas."]