WAEC Chemistry 2017 Paper

Concept:Acidic gases form acids when dissolved in water or react with water to produce acidic solutions.Explanation:$\mathrm{SO}_3$ dissolves in water to form sulphuric acid, so it is acidic.$\mathrm{NO}_2$ reacts with water to produce nitric acid and nitrous acid, so it is acidic.$\mathrm{CO}_2$ dissolves in water to form carbonic acid, so it is acidic.CO does not produce an acidic solution in water.It is therefore regarded as a neutral oxide among the given options.Answer:D. CO