Standard electrode potentials E ⦵ ; standard cell potentials E ⦵ cell and the Nernst equation

Summary

Standard Electrode Potential (E°) — A measure of the tendency of a half-cell to undergo reduction compared to the standard hydrogen electrode (SHE), which is assigned a value of 0.00 V. Example: The E° value for Br2/Br- is +1.09 V, indicating a strong tendency to be reduced. Standard Cell Potential (E°cell) — The voltage of an electrochemical cell made up of two half-cells, calculated using E°cell = E°reduction - E°oxidation. Example: For a cell with sodium and bromine half-cells, E°cell = +3.80 V. Nernst Equation — An equation used to calculate the electrode potential under non-standard conditions. Example: E = E° - (RT/zF) ln(Q), where Q is the reaction quotient.

Exam Tips

Key Definitions to Remember

• Standard Electrode Potential (E°)
• Standard Cell Potential (E°cell)
• Nernst Equation

Common Confusions

• Confusing the sign of E° values with the likelihood of reduction or oxidation.
• Misunderstanding the role of the standard hydrogen electrode as a reference.

Typical Exam Questions

• What is the standard electrode potential? It is the measure of a half-cell's tendency to undergo reduction compared to the standard hydrogen electrode.
• How do you calculate the standard cell potential? Use the formula E°cell = E°reduction - E°oxidation.
• What is the Nernst equation used for? It calculates the electrode potential under non-standard conditions.

What Examiners Usually Test

• Ability to calculate standard cell potentials.
• Understanding of how E° values predict the direction of electron flow.
• Application of the Nernst equation to non-standard conditions.