Electrochemistry Measurement of Electrode Potential Electrode Potential of Galvanic Cell The galvanic cell has two electrode potentials; anode potential and cathode potential. When the cell potential is measured with voltmeter, it gives the difference of both potentials but not an individual potential. Electrochemistry Measurement of Electrode Potential Electrode Potential of Galvanic Cell Electrochemistry Measurement of Electrode Potential Standard Electrode Potential It is impossible to measure the potential of just one electrode, but it can be circumvented by selecting a particular electrode as a standard electrode and assigning it a zero electrode potential and then measure the relative potential of an electrode in question in reference to that standard electrode potential. Electrochemistry Measurement of Electrode Potential Standard Electrode Potential The hydrogen electrode is chosen as the standard electrode that consists of hydrogen gas bubbled through platinum electrode at 1 atm into 1M hydrochloric acid at 25 o C that has assigned zero as a standard electrode potential. Electrochemistry Measurement of Electrode Potential Standard Electrode Potential Electrochemistry Measurement of Electrode Potential If we want to measure the standard electrode potential for zinc electrode, then we construct the cell according to the following cell diagram: Zn(s) | Zn 2+ (aq) || H + (1 M) I H 2 (1 atm) / Pt(s) and measure the electrode potential, which is 0.76 V at 25 o C. This also happens to be the standard potential for zinc electrode. Electrochemistry Measurement of Electrode Potential The given cell diagram is broken up into two half- reactions: Oxidation: Zn(s) Zn 2+ (1M) + 2e - Reduction: 2H + (1M ) + 2e - H 2 (1atm) Oxidation: Zn(s) Zn 2+ (1M) + 2e - Reduction: 2H + (1M ) + 2e - H 2 (1atm) By convention, the standard emf of the cell (E o cell) is the sum of oxidation and reduction potentials, is given by the following equation, E o cell = E o ox + E o red or 0.76 V = E o ox + 0 Thus, the standard oxidation potential for Zn is V. Electrochemistry Measurement of Electrode Potential Electrochemistry Measurement of Electrode Potential Standard Electrode Potentials at 298 K