Energetics & electrochemistry · HL
E°cell & ΔG° (HL)
Relate standard cell potential to Gibbs energy change.
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Number formats & units
Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.
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Result & working
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Interpretation & assumptions
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Formula & example
The relationship
What the variables mean
| Symbol | Meaning |
|---|---|
| Faraday constant ≈ 96485 C mol⁻¹. | |
| Moles of electrons transferred per stoichiometric reaction. |
Worked example
- Cathode E°red / V
- 0.34
- Anode E°red / V
- -0.76
- Electrons transferred n
- 2
1.1 V
Follow the example steps
- E°cell = E°cathode − E°anode = 0.34 − (-0.76) = 1.1 V
- ΔG° = −nFE° = −2 × 96485.33 × 1.1 = -212.2677 kJ mol⁻¹
Common mistakes
Subtract the anode reduction potential from the cathode reduction potential.
Incorrect approach
E°cell = 0.34 + (−0.76) = −0.42 V
Correct approach
E°cell = 0.34 − (−0.76) = 1.10 V
More checks before you submit
- Use reduction potentials consistently.
- n is the electron-transfer stoichiometry, not the coefficient of an arbitrary species.
Method notes
A positive E°cell gives negative ΔG° for the reaction written under standard conditions. Multiplying a half-equation does not multiply its electrode potential.