InterviewSolution
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InterviewSolution
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A mixture of two salts was treated as follows: (i) The mixture was heated with manganese dioxide and concentrated sulphuric acid when yellowish green gas was liberated. (ii) The mixture on heating with sodium hydroxide solution gave a gas which turned red litmus blue. (iii) Its solution in water gave blue precipitate with potassium ferricyanide and red colouration with ammonium thiocyanate. (iv) The mixture was boiled with potassium hydroxide and the liberated gas was bubbled through an alkaline solution of K_(2)Hgl_(2) to give brown precipitate. Identity the two salts. Give ionic equations for reactions involved in the tests (). (i) and (int). |
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Answer» Solution :(i) `2Cl^(-)+MnO_(2)+H_(2)SO_(4)(conc.)+2h^(+)toMnSO_(4)+UNDERSET(groon)underset(YELLOW wish)(Cl_(2)uarr)+2H_(2)O` (ii) `NH_(4)^(+)+2NaOHtoNH_(3)+H_(2)O+Na^(+)` (iii) `3Fe^(2+)+2[Fe(CN)_(6)]^(3-)toFe_(3)underset((blue ppt.))underset(Prussian blue)([Fe(CN_(6))]_(2))` (i) `Mixture+MnO_(2)+H_(2)SO_(4)(conc.)to` yellowish green gas M The reaction suggests thal the mixture contains `Cl^(-)` ions. `therefore 2Cl^(-)+MnO_(2)+H_(2)SO_(4)(conc.)+2H^(+)MnSO_(4)+underset(Yellowwish green)(CI_(2)uarr)+2H_(2)O` (ii) `Mixture+NaOHto` Gas turningred litmus blue The reaction suggests that the gas is ammonia (ie, basic in character turning red litmus blue). Ammonia will be evolved from an ammonium SALT. Thus, `NH_(4)^(+)+NaOHtoNH_(3)+H_(2)O+Na^(+)` (iii) Solution of mixture `+K_(2)[Fe(CN)_(6)] toblue ppt`. The reaction suggests that the mixture contains a Fe (II) of prussian blue complex. `3Fe^(2+)+2[Fe(CN)_(6)]^(3+)Fe_(3)underset((Blue ppt.))underset(Prussian blue) ([Fe(CN)_(6)]_(2))` Red colourless with ammonium thioyanate suggests that some Fe (III) is also present. It is likely that a part of Fe (II) is oxidized (III) by AIR. `Fe^(3+)+3NH_(4)SCN toFeunderset(“red colourless”)((SCN))+3NH_(4)^(+)` `2Fe^(2+)+[O]+2H^(+)to 2Fe^(3+)+H _(2)O` (iv) `Mixture+KOHtoGasoverset(K_(2)Hgl_(4))tobrown ppt`. the above reaction can be explained, when ammonia is liberated on boiling the mixture with potassium hydroxide. The liberated ammonia reacts with an alkaline solutions of `K_(2)Hgl_(4)` Hgle to giv a brown ppt. Hence, the mixture contains, `Fe^(2+)`,`NH_(4)^(+)` and cr ions (with an impurity of `Fe^(3+)` ions). The two salts are `FeCl_(2)` and `NH_(4)CI`. |
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