Question

The electrolysis of aqueous sodium chloride (brine) is an important industrial process for the production of chlorine and sodium hydroxide. In fact, this process is the second largest consumer of electricity in the United States, after the production of aluminum. Write a balanced equation for the electrolysis of aqueous sodium chloride (hydrogen gas is also produced).

Short answer

The balanced chemical equation for the electrolysis of aqueous sodium chloride is: \(2Cl^-(aq) + 2H_2O(l) \rightarrow Cl_2(g) + H_2(g) + 2OH^-(aq)\), which produces chlorine gas, hydrogen gas, and hydroxide ions.

Step-by-step solution

Write the half-reactions for the anode and the cathode

In the electrolysis process, oxidation happens at the anode and reduction at the cathode. For the electrolysis of aqueous sodium chloride, the half-reactions are as follows: Anode (oxidation): \(2Cl^-(aq) \rightarrow Cl_2(g) + 2e^-\) Cathode (reduction): \(2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)\)

Balance the electrons in the half-reactions

In this case, the number of electrons in the half-reactions is already balanced. Both half-reactions have 2 electrons each.

Combine the half-reactions to form the overall balanced equation

To obtain the overall balanced equation for the electrolysis of aqueous sodium chloride, we need to add the half-reactions for the anode and the cathode: \[2Cl^-(aq) + 2H_2O(l) \rightarrow Cl_2(g) + H_2(g) + 2OH^-(aq)\] This is the balanced chemical equation for the electrolysis of aqueous sodium chloride, producing chlorine gas, hydrogen gas, and hydroxide ions.