Molecular hydrogen is produced as a byproduct in the industrial production of NaOH by electrolysis of aq \(NaCl\) solution
\(NaCl → Na^+ + Cl^–\)
\(H_2O ⇌ H^+ + OH^-\)
Cathode : \(2H_2O + 2e → H_2 + 2OH^–\)
Anode : \(2Cl^– → Cl_2 +2e\)
\(NaOH\) is crystallised from the remaining part of electrolyte.
For the separation of two immiscible liquids, which method is used?

In the first configuration (1) as shown in the figure, four identical charges \( q_0 \) are kept at the corners A, B, C and D of square of side length \( a \). In the second configuration (2), the same charges are shifted to mid points C, E, H, and F of the square. If \( K = \frac{1}{4\pi \epsilon_0} \), the difference between the potential energies of configuration (2) and (1) is given by: