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How do you count forthe following observations ? (a) Though alkaline potassium permanganate and acidic potassium permanaganate both are used as oxidatns yet in the manufacture of benzoic acidfrom tolurene we use alcoholic ptoassum permanganate as an oxidant why write a balaced redox equation for the reaction (b) When concentrated suphuric acid is added to an inorganic mixutre containing chloride we get pungent smelling gas HCI but if the mixture contains bromide then we get red vapour of bromine why? |
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Answer» Solution :(a) Toluene can be oxidised to benczoic ACID in acidic basic and neutral media according to the following redox equation (i) acidic medium  in the laboratory benzoic acid is usually prepared by alkaline `KMnO_(4)` oxidation of toluene however in industry alcoholic `KMnO_(4)` is preferred to acid or alkaline `KMnO_(4)` because of the following reasons (i) The cost of adding an acid or the base is avoided because in the neutral medium the base `(OH^(-)ion)` are produced in the reaction itself (ii) since rection occur faster in HOMOGENEOUS medium than in HETEROGENEOUS medium therefore alcohol helps in mixing the tworectants i.e `KMnO_(4)` and toluene (b) when conc `H_(2)SO_(2)`is added to an inorganic mixture CONTAING chloride a pungent smelling gas hci is produced because a stronger acid displace a weaker acid from its salt `2 NaCI+2H_(2)SO_(4)rarr2NaSO_(4)+2HCI` `2 HCI+H_(2)SO_(4)rarrCI_(2)+SO_(2)+2H_(2)O` however when the mixture contains bromide ion the initally produced HBr beinga stronger REDUCING agent than HCI reduces `H_(2)SO_(4)`to `SO_(2)` and is itself oxidised to produce red vapour of `Br_(2)` `2 NaBr +2 H_(2)SO_(4)rarr2NaHSO_(4)+2 HBr` `2HBr+H_(2)SO_(4)rarrBr_(2)+SO_(2)+2H_(2)O` |
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