In dilute aqueous sodium bromide (NaBr) solution, when an electric current is passed through it during electrolysis, the following half-reactions occur at the anode and cathode:
At the anode (positive electrode):
2Br- (aq) → Br2 (g) + 2e-
This half-reaction involves the oxidation of bromide ions (Br-) to elemental bromine (Br2). The bromine gas is liberated at the anode.
At the cathode (negative electrode):
2H2O (l) + 2e- → H2 (g) + 2OH- (aq)
This half-reaction involves the reduction of water molecules (H2O) to produce hydrogen gas (H2) and hydroxide ions (OH-).
Overall, the electrolysis of dilute aqueous sodium bromide produces bromine gas at the anode and hydrogen gas at the cathode, along with sodium ions (Na+) and hydroxide ions (OH-) remaining in the solution.