Statement I: In case of Hg cathode Na⁺ undergoes deposition

Statement II: Nature of electrode determines the deposition order

Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I

The correct answer is: 1. Both Statement I and Statement II are correct, and Statement II is the correct explanation of Statement I.

Statement I is correct: When a mercury (Hg) cathode is used in an electrolytic cell, sodium ions (Na+) can undergo deposition at the cathode. This is because mercury has a lower reduction potential compared to sodium. The reduction of sodium ions occurs at the cathode during the electrolysis, and metallic sodium is formed as a result.

Statement II is the correct explanation of Statement I:  The nature of the electrode indeed determines the deposition order in an electrolytic cell. The deposition of ions during electrolysis is governed by the standard electrode potentials of the involved species. The species with a lower reduction potential (more positive standard electrode potential) is preferentially reduced and deposited at the electrode.

In this case, since mercury has a lower reduction potential than sodium, it will facilitate the reduction of sodium ions (Na⁺) at the cathode, leading to the deposition of metallic sodium (Na) on the mercury electrode.

Therefore, both statements are correct, and Statement II provides the correct explanation for why sodium deposition occurs at the mercury cathode. Option 1 is the correct choice.