In an electrolytic cell, the negative terminal is the cathode and is the site of the reduction half-reaction. Which alternative statement is true?

• A. cathode and oxidation
• B. anode and reduction
• C. cathode and reduction
• D. anode and oxidation

Answer: (C)

In an electrolytic cell, the external power source drives electrons into the circuit, so the electrode connected to the negative terminal becomes the cathode. At the cathode, reduction occurs—ions gain electrons drawn from the external circuit, forming reduced species. The opposite electrode, the anode, is connected to the positive terminal and is where oxidation happens, with electrons being released from species there. Because the question specifies that the negative terminal is the cathode and that site is where reduction occurs, that pairing is correct. The statement that the cathode is associated with oxidation would mix up the fundamental roles, and saying the anode performs reduction contradicts the defined locations, even though oxidation does occur at the anode. The true pairing given is cathode with reduction.