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Name the processes from which chlorine is obtained as a by-product. What will happen if an aqueous solution of NaCl is subjected to electrolysis ? |
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Answer» Solution :Down.s PROCESS is used for PREPARATION of sodium metal where dichlorine is OBTAINED as a by-product. In this process, molten NaCl containing `CaCl_2` (flux) is electrolysed. `CaCl_2` lowers the melting point of NaCl. `NaCl_((l))overset(873 K)(rarr) Na_((l))^(+) + Cl_((l))^(+)` Cathode : `2Na_((l))^(+) + 2E^(-) to 2Na_((l))` Anode : `2Cl_((l))^(-) to Cl_(2(g)) + 2e^(-)` (ii) When aqueous NaCl is electrolysed `H_2` is evolved at cathode an `Cl_2` at anode. The `H_2` is evolved because `E_(H_2O//H_2)^(Theta)`is less negative than `E_(Na^(+)//Na)^(Theta)`Thus, preferentially, water will be reduced to H, at cathode. Anode : `2Cl_((aq))^(-) to Cl_(2(g)) + 2e^(-)` Cathode : `2H_2 O_((l)) + 2e^(-) to H_(2(g)) + 2OH_((aq))^(-)`. |
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