What is a half-cell reaction?

A half-cell reaction refers specifically to the individual oxidation or reduction processes that take place at one electrode in an electrochemical cell. In the context of an electrochemical cell, two half-cell reactions occur: one at the anode, where oxidation happens, and one at the cathode, where reduction takes place. These half-cell reactions are critical because they help us understand the overall cell reaction and the flow of electrons between the electrodes.

The correct answer highlights the distinction between the two processes in a cell, emphasizing that a half-cell reaction is focused on just one part of the overall electrochemical reaction. This concept allows for the analysis and representation of electrochemical processes independently, which is fundamental for designing and studying batteries, fuel cells, and electrolysis systems.