Question

In electrolysis of NaCl when Pt electrode is taken then$H_2$ is liberated at cathode while with Hg cathode it forms sodium amalgam:

• A. Hg is more inert than Pt
• B. More voltage is required to reduce $H^{+}$ at Hg than a Pt
• C. Na is dissolved in Hg while it does not dissolve in Pt
• D. Conc of $H^{+}$ ions is larger when Pt electrode is taken.

Answer 1

The correct option is D Conc of $H^{+}$ ions is larger when Pt electrode is taken.

In electrolysis of NaCl when Pt electrode is taken thenH2 is liberated at cathode while with Hg cathode it forms sodium amalgam.
Conc of H+ ions is larger when Pt electrode is taken. Hence, H+ ions are discharged in preference to Na+ ions. When Hg cathode is used Na+ ions are discharged.