describe the colours and the trend in volatility of chlorine, bromine and iodine

explain, including by use of an equation, the use of chlorine in water purification to include the production of the active species HOCI and CIO\(^-\) which kill bacteria

describe and explain the reactions of halide ions with: (a) aqueous silver ions followed by aqueous ammonia (the formation and formula of the \([Ag(NH_3)_2]^+\) complex is not required) (b) concentrated sulfuric acid, to include balanced chemical equations