What are the products obtained on adding ammonia solution to zinc sulphate solution (precipitation reaction)?
A solution of zinc sulphate in water contains zinc ions and sulphate ions. A solution of ammonia mainly contains ammonia molecules mixed with water molecules but a small proportion of the ammonia (a weak base) reacts with water to produce ammonium ions and hydroxide ions. On mixing the two solutions a white precipitate forms. This is zinc hydroxide which is insoluble in water. Ammonium and sulphate ions do not form a precipitate because ammonium sulphate is soluble in water. So the ammonia and sulphate ions are spectator ions – they stay in solution. If you add excess ammonia solution the white precipitate redissolves because ammonia molecules forms a stable complex with zinc ions. Risk assessment Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority
