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 the following reactions of alkenes: (a) the electrophilic addition of (i) hydrogen in a hydrogenation reaction, \( H_2(g) \) and Pt/Ni catalyst and heat (ii) steam, \( H_2O(g) \) and \( H_3PO_4 \) catalyst (iii) a hydrogen halide, \( HX(g) \), at room temperature (iv) a halogen, \( X_2 \) (b) the oxidation by cold dilute acidified \( KMnO_4 \) to form the diol (c) the oxidation by hot concentrated acidified \( KMnO_4 \) leading to the rupture of the carbon–carbon double bond and the identities of the subsequent products to determine the position of alkene linkages in larger molecules (d) addition polymerisation exemplified by the reactions of ethene and propene