Relationship between Gibbs Energy Change and Cell Potential
Explore the fundamental thermodynamic relationship connecting the Gibbs energy change (ΔG) of a reaction to the cell potential (Ecell) of an electrochemical cell.
What is Relationship between Gibbs Energy Change and Cell Potential?
A thermodynamic potential that measures the maximum amount of non-expansion work that can be extracted from a closed system at constant temperature and pressure. Its sign indicates spontaneity: ΔG < 0 for spontaneous, ΔG > 0 for non-spontaneous, and ΔG = 0 for equilibrium.
Key formula / rule: Relationship between Gibbs Energy Change and Cell Potential
Key points
- To understand the thermodynamic basis of electrochemical cell operation.
- To calculate Gibbs energy change from cell potential, and vice versa.
- To predict the spontaneity of redox reactions using cell potential.
- To apply the relationship under standard and non-standard conditions.
Common exam trap
Forgetting the negative sign in the equation (ΔG = -nFEcell).
Definitions
- Term
Gibbs Energy Change (ΔG)
- Meaning
A thermodynamic potential that measures the maximum amount of non-expansion work that can be extracted from a closed system at constant temperature and pressure. Its sign indicates spontaneity: ΔG < 0 for spontaneous, ΔG > 0 for non-spontaneous, and ΔG = 0 for equilibrium.
- Term
Cell Potential (Ecell)
- Meaning
The difference in electric potential between the two electrodes of an electrochemical cell. It is the driving force for the flow of electrons and is measured in volts.
- Term
Faraday's Constant (F)
- Meaning
The magnitude of electric charge per mole of electrons. It is approximately 96485 coulombs per mole (C/mol).
Learning objectives
To understand the thermodynamic basis of electrochemical cell operation.
To calculate Gibbs energy change from cell potential, and vice versa.
To predict the spontaneity of redox reactions using cell potential.
To apply the relationship under standard and non-standard conditions.
Formulae
- Name
Relationship between Gibbs Energy Change and Cell Potential
- Note
ΔG is the Gibbs energy change, n is the number of moles of electrons transferred, F is Faraday's constant, and Ecell is the cell potential.
- Expression
ΔG = -nFEcell
- Name
Relationship under Standard Conditions
- Note
ΔG° is the standard Gibbs energy change, and E°cell is the standard cell potential.
- Expression
ΔG° = -nFE°cell
Prerequisites
Understanding of Gibbs Free Energy (ΔG) and its relation to spontaneity.
Basic knowledge of electrochemical cells (anode, cathode, cell potential).
Concept of redox reactions and electron transfer.
Faraday's constant.
Common mistakes
Forgetting the negative sign in the equation (ΔG = -nFEcell).
Incorrectly identifying the number of electrons (n) transferred in the redox reaction.
Confusing standard conditions (ΔG°, E°cell) with non-standard conditions.
Assuming Ecell is always positive for a spontaneous reaction without considering the sign of ΔG.
Keywords
Gibbs Energy
Cell Potential
Spontaneity
Electrochemical Cell
Faraday's Constant
Thermodynamics
Redox Reaction
Standard Conditions
Practice preview
What is the correct relationship between Gibbs energy change (ΔG) and standard cell potential (E°cell) for an electrochemical reaction?…
easy
In the equation ΔG = -nFEcell, what are the standard units for Gibbs energy change (ΔG) if Ecell is in Volts and F is in Coulombs per mole?…
easy
For a spontaneous electrochemical reaction, which of the following conditions is true regarding Gibbs energy change (ΔG) and cell potential (Ecell)?…
easy