Question

A potential difference of 0.25 volts is observed when an electrode system M/M²⁺ (1 mol L⁻¹) is connected to a standard hydrogen electrode. If the direction of the flow of current is from hydrogen electrode to the metal electrode, calculate the standard potential of the electrode.

Answer 1

Given: Electrode system = M/M²⁺ (1 M)

Connected to Standard Hydrogen Electrode (SHE) (E°) = 0.00 V

Potential difference = 0.25 V

Current flows from the SHE to the M electrode.

\[\ce{E^{\circ}_{cell} = E^{\circ}_{cathode} - E^{\circ}_{anode}}\]

\[\ce{0.25 = E^{\circ}_{SHE} - E_{M/M^{2+}}}\]

\[\ce{0.25 = 0 - E_{M/M^{2+}}}\]

\[\ce{E_{M/M^{2+}}}\] = −0.25 V

∴ The standard potential of an electrode is −0.25 V.