Ncert Exercises & Solutions

How will the pH of brine (aq NaCl solution) be affected when it is electrolysed?

The pH of the solution will rise as NaOHis formedin the electrolytic cell.

Chemical reaction occurring at cell when aqueous brine solution is electrolysed are as follows

NaCl (aq) \overset{H_{2} O}{⟶} {Na}^{+} (aq) + {Cl}^{-} (aq)

Cathode

H_{2} O (l) + e^{-} ⟶ \frac{1}{2} H_{2} (g) + {OH}^{-} (aq)

Anode

{Cl}^{-} (aq) ⟶ \frac{1}{2} {Cl}_{2} (g) + e^{-}

Net reaction

NaCl (a q) + H_{2} O (l) ⟶ {Na}^{+} (a q) + {OH}^{-} (a q) + \frac{1}{2} H_{2} + \frac{1}{2} {Cl}_{2}