Question

Why is an external emf of more than 2.2 V required for the extraction of \[\ce{Cl2}\] from brine?

Answer 1

For the reaction of extraction of \[\ce{Cl2}\] from brine solution:

\[\ce{2Cl^{-} (aq) + 2H2O(l) -> 2OH^{-} (aq) + H2(g) + Cl2(g)}\] the value of ΔG^Θ is + ve (442 kJ).

For this value of E^– is ΔG^Θ = – nFE^Θ 

or E° = ` - (ΔG^circ)/(nF) = - (422 xx 10^3J)/(2 xx 96500)` = – 2.20 V

Therefore, extraction of \[\ce{Cl2}\] from brine solution will require an external emf more than 2.20 V for electrolysis is process.