Electrode potentials are sensitive to factors including electrode composition, electrolyte composition, temperature, degree of agitation, presence of depolarizers or inhibitors, surface conditions of electrodes, and metallurgical conditions of electrodes. Which of the following is NOT a factor?

• A. Ambient light
• B. Electrode composition
• C. Temperature
• D. Presence of depolarizers or inhibitors

Answer: (A)

Ambient light does not affect electrode potentials in typical electrochemical measurements because the potential is set by the chemical equilibrium at the electrode interface, not by photons. The intrinsic redox behavior comes from electrode composition, which defines the specific redox couple and its standard potential. The electrolyte composition changes the activities of the reacting ions and thus the potential through the Nernst relationship. Temperature alters the kinetics and thermodynamics of the reaction, affecting the potential via the RT/F term and activity coefficients. Degree of agitation influences mass transport and concentration polarization, which can shift the measured potential. The presence of depolarizers or inhibitors changes the reaction kinetics and can alter overpotentials, thereby modifying the observed potential. Surface conditions and metallurgical state of the electrode determine the active surface and the actual redox species available at the interface. Outside of photoelectrochemical systems or light-sensitive reactions, ambient light isn’t a factor in establishing electrode potentials, so it’s not considered one of the influencing factors.