International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What type of reaction occurs at the cathode during electrolysis?

1. Oxidation

2. Reduction

3. Combustion

4. Decomposition

The correct answer is: Reduction

During electrolysis, the cathode is the electrode where reduction occurs. This is because the cathode is the site where positive ions gain electrons. The process of reduction involves the decrease of oxidation state of these ions, often resulting in the formation of a neutral atom or molecule as they gain electrons. For example, in the electrolysis of water, hydrogen ions (H⁺) move towards the cathode, where they gain electrons (reduction) and form hydrogen gas (H₂). This behavior is fundamental to the process and distinguishes the role of the cathode compared to the anode, where oxidation takes place. Understanding that reduction occurs at the cathode is crucial in electrolysis, as it helps in predicting the products formed during the process based on the nature of the electrolyte and the electrodes used.