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

Options

A. ` C l ^( - ) (aq) to (1)/(2) Cl _ 2 (g) + e ^( - ) , E ^( @ )""_("Cell") = 1.36 V `
B. `2 H_2 O (l ) to O _ 2 (g) + 4H^(+) + 4 e^(- ) , E^(@)""_("Cell") = 1.23 V `
C. ` Na ^( + ) (aq) + e ^( -) to Na (s) , E ^(@)""_("cell") = 2.71 V `
D. ` H ^(+ ) (aq) + e ^(- ) to (1)/(2) H _ 2 O (g), E^(@)""_("cell") = 0.00 V `

Answer

A

Explanation

Although oxidation potential of ` Cl ^(-)` ions is higher than that of ` H _ 2 O `, yet oxidation of ` Cl ^- ` ions occurs in preference to ` H _ 2 O ` since due to overvoltage of ` O _ 2 ` (i.e., water needs greater voltage for oxidation to ` O _ 2 ` as it is a kinetically slow process) much higher potential than ` 1* 36 ` V is actually needed for the oxidation of ` Cl^(-) ` ions to ` Cl_ 2 `.