During the electrolysis of a dilute solution of NaCl, what is produced at the anode?

Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction. In the electrolysis of a dilute solution of sodium chloride (NaCl), ions present in the solution migrate towards electrodes based on their charge. Positive ions, or cations, move toward the cathode (negative electrode), while negative ions, or anions, move toward the anode (positive electrode).

In a dilute NaCl solution, the main ions are Na⁺, H⁺, Cl⁻, and OH⁻. At the cathode, H⁺ ions from water are more easily reduced than Na⁺ ions, so hydrogen gas is produced at the cathode.

At the anode, Cl⁻ ions from sodium chloride are oxidized. Oxidation involves the loss of electrons, and the reaction at the anode can be written as:

2Cl⁻ → Cl₂ + 2e⁻

This produces chlorine gas, which bubbles off at the anode. Oxygen is not formed because OH⁻ ions are less easily oxidized than Cl⁻ ions in a dilute solution. Sodium metal is never produced at the anode in aqueous solution because it reacts immediately with water.

Understanding the products of electrolysis is important in industrial chemistry. The electrolysis of brine is used to produce chlorine gas, hydrogen gas, and sodium hydroxide, which are key chemicals in industries such as soap making, PVC production, and paper bleaching.

The key concept here is that the more easily oxidized ion is discharged at the anode. In dilute NaCl solution, Cl⁻ is more easily oxidized than OH⁻, making chlorine the product at the anode.