How do you count for the following observations ?
(a) Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why ? Write a balanced redox equation for the reaction.
(b) When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why ?

Explanation

Alcohol will act as a solvent for toluene which is insoluble in aqueous medium.
(a) `C_(6)H_(5)CH_(2) + 2KMnO_(4) rarr C_(6)H_(5)COOH + 2MnO_(2) + 2KOH`
(b) (i) `H_(2)SO_(4) + Cl^(-) rarr HCl + HSO_(4)^(-)`
(ii) `H_(2)SO_(4) + Br^(-) rarr HBr + HSO_(4)^(-)`
`H_(2)SO_(4) 2HBr rarr Br_(2) + SO_(2) + 2H_(2)O`