What is the purpose of a reference electrode and give two common examples with typical potential values?

• A. To measure current directly; examples: SHE and Ag/AgCl.
• B. To provide a stable, known reference potential; examples: SHE (0 V), Ag/AgCl in saturated KCl (~+0.197 V vs SHE) and SCE (~+0.241 V vs SHE).
• C. To bias the electrode potential using a separate cell.
• D. To calibrate the voltmeter.

Answer: (B)

A reference electrode provides a stable, known potential that does not depend on the reaction happening at the working electrode, so it acts as a fixed zero point for measuring or controlling the working electrode's potential. In practice, this allows the voltmeter or potentiostat to compare the working electrode against a constant reference, while injecting current into the system without the reference potential drifting significantly.

Two common examples are the Standard Hydrogen Electrode, which is defined to be 0 V by convention at 25°C, and a silver/silver chloride electrode in saturated KCl, which sits at about +0.197 V relative to the Standard Hydrogen Electrode (also at 25°C). This reference stability and these well-known potentials enable accurate interpretation of the working electrode’s behavior during measurements.