What is the effect of adding a supporting electrolyte in a redox experiment?

• A. It changes the standard potential of the redox couple.
• B. It increases conductivity, reduces migration effects, and stabilizes the potential.
• C. It decreases the current response.
• D. It accelerates electrode dissolution.

Answer: (B)

Adding a supporting electrolyte in a redox experiment provides inert ions that raise the solution’s ionic strength. This increases conductivity, reducing the ohmic (iR) drop between the electrode and the solution, so the measured potential more accurately reflects the true electrode potential. It also suppresses ion migration under the applied field because the plentiful counter-ions resist redistribution, keeping the concentration of reactive species near the electrode from changing due to migration. With migration minimized, the potential remains more stable and the current response becomes governed mainly by diffusion and kinetics rather than migration. The standard potential of the redox couple is a thermodynamic property set by the couple itself and is not altered by the inert electrolyte. It doesn’t inherently decrease the current or hasten electrode dissolution; it can even allow larger currents by lowering resistance.