What gas is formed at the anode during the electrolysis of sodium chloride solution?

During the electrolysis of sodium chloride solution, the process involves breaking down the sodium chloride (NaCl) into its constituent ions, sodium ions (Na⁺) and chloride ions (Cl⁻), when an electric current is passed through the solution.

At the anode, which is the positive electrode, oxidation occurs. In the case of the electrolysis of sodium chloride solution, the chloride ions are oxidized. This reaction leads to the release of chlorine gas (Cl₂). The half-reaction at the anode can be represented as:

2Cl⁻ → Cl₂ + 2e⁻

As a result, chlorine gas is produced at the anode.

The other gases listed, such as oxygen and hydrogen, are more relevant in the context of electrolysis of water or other specific reactions. Oxygen is typically generated at the anode during the electrolysis of water, while hydrogen is produced at the cathode during both the electrolysis of water and salt solutions. Nitrogen does not play a role in this particular electrolysis process regarding the formation of gases at the electrodes. Therefore, the gas formed at the anode during the electrolysis of sodium chloride solution is indeed chlorine.