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Account for the following : (a) Chlorine water has both oxidising and bleaching properties. (b) H_(3)PO_(2) and H_(3)PO_(3) act as good reducing agents while H_(3)PO_(4) does not. (c) On addition of ozone gas to KI solution, violet vapours are obtained. |
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Answer» Solution :(a) In presence of moisture or water, `Cl_(2)` gives nascent oxygen which is responsible for its oxidising and bleaching properties as SHOWN below : `Cl_(2) + H_(2)O rarr ,HCl + HClO' rarr 2HCl + underset("Nascent oxygen")([O])` (i) It oxidises acidified ferrous sulphate to ferric sulphate `{:(""Cl_(2)+H_(2)O rarr 2HCl + O),(" "FeSO_(4)+H_(2)SO_(4) + O rarr Fe_(2)(SO_(4))_(3)+H_(2)O),(bar (underset(("Green"))(2FeSO_(4))+H_(2)SO_(4) + Cl_(2) rarr underset(("Brown"))(Fe_(2)(SO_(4))_(3))+2HCl)):}` (ii) It bleaches vegetable and ORGANIC colouring matter to colourless SUBSTANCES by oxidation `Cl_(2) + H_(2)O rarr 2HCl + [O]` Vegetable colouring matter `+ O rarr` Oxidised colourless substances. (b) The structures of `H_(3)PO_(2), H_(3)PO_(3) and H_(3)PO_(4)` are : Due to the presence of P-H bonds, both `H_(3)PO_(2) and H_(3)PO_(3)` act as reducing agents. In contrast, `H_(3)PO_(4)` does not have any P-H bonds and hence it does not act as a reducing agent.  (c) `O_(3)` is a POWERFUL oxidising agent. Therefore, it oxidises aq. KI to violet vapours of `I_(2)` `{:(""O_(3)(g) rarr O_(2)(g) + O(g)),(""2KI (aq) + H_(2)O (l) + O(g) rarr 2KOH (aq) + I_(2)(s)),(bar(underset(("Colourless"))underset("Potassium iodide")(2KI(aq))+H_(2)O (l) + O_(3)(g) rarr 2KOH (aq) + O_(2)(g)+underset(("Violet"))underset("Iodine")(I_(2)(s)))):}` |
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