Brine is electrolysed by using inert electrodes. The reaction at anode is_______

Options

A. `Cl^(-)(aq) to(1)/(2)Cl_(2)(g)+e^(-)," "E_("Cell")^(ө)=1.36 V`
B. `2H_(2)O(l) to O_(2)(g)+4H^(+)+4e^(-)," "E_("Cell")^(ө)=1.23 V`
C. `Na^(+)(aq)+e^(-)to Na(s)," "E_("Cell")^(ө)=2.71 V`
D. `H^(+)(aq)+e^(-) to (1)/(2)H_(2)(g)," "E_("Cell")^(ө)=0.00 V`

Answer

A

Explanation

(a) Brine is electrolysed by using insert electrodes. The possible reactions occuring at anode are
`Cl^(-)(aq) to (1)/(2)Cl_(2)(g)+e^(-)," "E_("Cell")^(ө)=1.36 V`
`2H_(2)L(l) to O_(2)(g)+4H^(+) + 4e^(-)," "E_("Cell")^(ө)=1.23 V`
The reaction at anode with lower value of `E^(@)` is preferred and therefore water should get oxidised in preference to `Cl^(-) (aq)` However `Cl_(2)` is produced instead of `O_(2)` . This unexpected result is explained on the basis of the fact that water needs greater voltage for oxidation to `O_(2)` (as it kinetically slow process) than that needed for oxidation of `Cl^(-)`ions to `Cl_(2)`