During the electrolysis of a dilute potassium bromide (KBr) solution, the following half-reactions occur at the electrodes:
At the Anode (Positive Electrode): The oxidation of negatively charged ions or anions occurs at the anode. In this case, bromide ions (Br-) are oxidized. The half-equation at the anode is:
2Br- -> Br2 + 2e-
This means that two bromide ions lose two electrons each to form one molecule of bromine gas (Br2).
At the Cathode (Negative Electrode): The reduction of positively charged ions or cations takes place at the cathode. In this case, potassium ions (K+) are reduced. The half-equation at the cathode is:
2H2O + 2e- -> H2 + 2OH-
This equation shows that water (H2O) is reduced by gaining two electrons to produce hydrogen gas (H2) and hydroxide ions (OH-).
Overall, the electrolysis of a dilute potassium bromide solution produces bromine gas at the anode and hydrogen gas and hydroxide ions at the cathode.