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

explain and use the terms oxidising agent and reducing agent