Aq NaCl because in aqueous condition at cathode first group and second group element are not deposited so H2 will deposit at cathode.

Answer:

Introduction:
In electrolysis, the passage of an electric current through an electrolyte solution causes chemical reactions at the electrodes. These reactions involve the transfer of electrons and the formation of new substances. The electrolyte used in the given scenario is capable of dissociating into ions.

Explanation:

Electrolysis of Sodium Chloride (NaCl):
- The given electrolytic solution is NaCl, which is a strong electrolyte. When NaCl is dissolved in water, it dissociates into Na+ and Cl- ions.
- During electrolysis, at the cathode (negative electrode), reduction occurs. The positively charged ions (cations) are attracted to the cathode and gain electrons to form neutral atoms or molecules.
- In the case of NaCl, Na+ ions are attracted to the cathode. However, the reduction potential of hydrogen ions (H+) is lower than that of Na+ ions. Therefore, H+ ions from the water are reduced instead of Na+ ions.
- The reduction of H+ ions results in the formation of H2 gas at the cathode. This is known as hydrogen evolution.

Electrolysis of Hydrochloric Acid (H2SO4):
- H2SO4 is a strong acid and a strong electrolyte. When it is dissolved in water, it dissociates into H+ and SO4-2 ions.
- Similar to the previous case, H+ ions are reduced at the cathode. However, the reduction potential of hydrogen ions is lower than that of H+ ions from H2SO4, so hydrogen gas is evolved at the cathode.
- The evolution of H2 gas occurs because the reduction potential of H+ ions is lower compared to other ions present in the electrolyte.

Conclusion:
- The given electrolytic solution is NaCl, in which the evolution of H2 gas occurs at the cathode during electrolysis.
- This happens because the reduction potential of hydrogen ions is lower than that of Na+ ions or other ions present in the electrolyte.
- Therefore, option 'C' (A NaCl) is the correct answer.