InterviewSolution
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InterviewSolution
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Predict the products of electrolysis in eaCHM of the following `:` `a.` An aqueous solution of `AgNO_(3)` with silver electrodes. `b.` An aqeous solution of `AgNO_(3)` with platinum electrodes, `c.` A dilute solution of `H_(2)SSO_(4)` with platinum electrodes. `d.` An aqueous solution of `CuCl_(2)` with platinum electrodes. |
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Answer» (i) `AgNO_(3)` ionizes in aqueous solutions to form `Ag^(+)` and `NO_(3)^(-)` ions . On On electrolysis, either `Ag_(+)` ions or `H_(2)O` molecules can be reduced at the cathode. But the reduction potential of `Ag_(+)` ions is higher than that of `H_(2)O`. `Ag_((aq))^(+) + e^(-) to Ag_((s)) , E^(@) = +0.80 V ` `2H_(2)O_((l)) + 2 e^(-) to H_(2 (g)) + 2 OH_((aq))^(-) , E^(@) = - 0.83 V` Hence `Ag^(+)` ions are reduced at the cathode . Similarly , Ag metal or `H_(2)O` molecules can be oxidized at the anode . But the oxidation potential of Ag is higher than that of `H_(2)O ` molecules . `Ag_((s)) to Ag_((aq))^(+) + e^(-) , E^(@) = - 0.80 V` `2H_(2)O_((l)) to O_(2 (g)) + 4 H_((aq))^(+) + 4 e^(-) , E^(@) = -1.23 V` Therefore , Ag metal gets oxidized at the anode . (ii) Pt cannot be oxidized easily . Hence , at the anode , oxidation of water occurs to liberate `O_(2)` . At the cathode , `Ag^(+)` ions are reduced and get deposited . (iii) `H_(2)SO_(4)` ionizes in aqueous solutions to give `H^(+)` and `SO_(4)^(-)` ions . `H_(2)SO_(4 (aq)) to 2H_((aq))^(+) + SO_(4 (aq))^(2-)` On electrolysis , either of `H^(+)` ions or `H_(2)O` molecules can get reduced at the cathode . But the reduction potential of `H^(+)` ions is higher than that of `H_(2)O` molecules . `2H_((ag))^(+) + 2e^(-) to H_(2 (g)) , E^(@) = 0.0V` `2H_(2)O_((aq)) + 2e^(-) to H_(2 (g)) + 2OH_((aq))^(-) , E^(@) = -0.83 V` Hence , at the cathode , `H^(+)` ions are reduced to liberate `H_(2)` gas . On the other hand , at the anode , either of `SO_(4)^(2-)` ions or `H_(2)O` molecules can get oxidized . But the oxidation of `SO_(4)^(2-)` involves breaking of more bonds than that of `H_(2)O` molecules . Hence , `SO_(4)^(2-)` ions have a lower oxidation potential than `H_(2)O` . Thus `H_(2)O` is oxidized at the anode to liberate `O_(2)` molecules . (iv) In aqueous solutions , `CuCl_(2)` ionizes to give `Cu^(2+)` and `Cl^(-)` ions as : `CuCl_(2 (aq)) to Cu_((aq))^(2+) + 2Cl_((aq))^(-)` On electrolysis , either of `Cu^(2+)` ions or `H_(2)O` molecules can get reduced at the cathode . But the reduction potential of `H^(+)` ions is higher than that of `H_(2)O` molecules . `2H_((aq))^(+) + 2e^(-) to H_(2(g)) , E^(@) = 0.0V` `2H_(2)O_((aq))k + 2e^(-) to H_(2 (g)) + 2OH_((aq))^(-) , E^(@) =- 0.83 V` . Hence , at the cathode , `H^(+)` ions are reduced to liberate `H_(2)` gas . On other hand , at the anode , either of `SO_(4)^(2-)` ions or `H_(2)O` molecules can get oxidized . But the oxidation of `SO_(4)^(2-)` involves breaking of more bonds than that of `H_(2)O` molecules . Hence , `SO_(4)^(2-)` ions have a lower oxidation potential than `H_(2)O` . Thus , `H_(2)O` is oxidized at the anode to liberate `O_(2)` molecules . (iv ) In aqueous solutions , `CuCl_(2)` ionizes to give `Cu^(2+)` and `Cl^(-)` ions as : `CuCl_(2(aq)) to Cu_((aq))^(2+) + 2Cl_((aq))^(-)` On electrolysis , either of `Cu^(2+)` ions or `H_(2)O` molecules can get reduced at the cathode . But the reduction potential of `Cu^(2+)` is more than that of `H_(2)O` molecules . `Cu_((aq))^(2+) + 2e^(-) to Cu_((aq)) , E^(@) = - 0.34 V` `H_(2)O_((l)) + 2e^(-) to H_(2(g)) + 2OH^(-) , E^(@) = - 0.83 V` Hence `Cu^(2+)` ions are reduced at the cathode and get deposited . Similarly , at the anode , either of `Cl^(-)` or `H_(2)O` is oxidized . The oxidation potential of `H_(2)O` is higher than that of `Cl^(-)` . `2Cl_((aq))^(-) to Cl_(2 (aq)) + 2e^(-) , E^(@) = - 1.36V` `2H_(2)O_((l)) to O_(2 (g)) + 4H_((aq))^(-) + 4e^(-) , E^(@) = -1.23 V ` But the oxidation of `H_(2)O` molecules occurs at a lower electrode potential than that of `Cl^(-)` ions because of over- voltage (extra voltage required to liberate gas ). As a result , `Cl^(-)` ions are oxidized at the anode to liberate `Cl_(2)` gas . |
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