Electrochemical Cell
Galvanic (voltaic) cells convert chemical energy to electrical energy; electrolytic cells use electrical energy to drive non-spontaneous reactions. Standard potentials determine spontaneity and cell EMF.
Why This Chemistry Calculation Matters
Why: Electrochemical cells power batteries, fuel cells, and corrosion processes. Understanding E° and spontaneity is essential for energy storage and materials design.
How: E°cell = E°cathode - E°anode. If E° > 0, the reaction is spontaneous (galvanic). Use Nernst equation for non-standard conditions.
- ●Daniell cell (Zn-Cu): E° = 1.10 V. Lead-acid: E° ≈ 2.05 V.
- ●ΔG° = -nFE° links cell potential to thermodynamic spontaneity.
- ●K = exp(nFE°/RT) gives equilibrium constant from E°.
- ●Electrolytic cells require applied voltage > |E°| to run.
Sample Electrochemical Cells
🔋 Zn-Cu Galvanic Cell
Classic Daniell cell: Zn|Zn²⁺||Cu²⁺|Cu, E° = 1.10 V
⚡ Ag-Pb Cell
Silver-lead cell: Pb|Pb²⁺||Ag⁺|Ag, E° = 0.93 V
⚡ Hydrogen-Oxygen Fuel Cell
Fuel cell: H₂|H⁺||O₂|H₂O, E° = 1.23 V
🔋 Alkaline Battery (Zn-MnO₂)
Zn|Zn²⁺||MnO₄⁻|Mn²⁺, E° = 2.27 V
🔋 Lead-Acid Battery
Pb|PbSO₄||PbO₂|PbSO₄, E° ≈ 2.05 V
🔋 Lithium-Ion Battery
Li|Li⁺||CoO₂|LiCoO₂, E° ≈ 3.7 V
⚙️ Custom Potentials
Calculate from custom E° values
Calculate Cell Potential
Nernst Equation (Optional)
Calculate cell potential at non-standard conditions using concentrations or reaction quotient
⚠️For educational and informational purposes only. Verify with a qualified professional.
🔬 Chemistry Facts
Galvanic cells: spontaneous; electrolytic: non-spontaneous.
— IUPAC
E°cell > 0 → spontaneous; E°cell < 0 → requires energy.
— Electrochemistry
Standard potentials measured vs. SHE (E° = 0 V).
— NIST
More positive E° = stronger oxidizing agent.
— Redox
What is an Electrochemical Cell?
An electrochemical cell is a device that converts chemical energy into electrical energy (galvanic/voltaic cell) or uses electrical energy to drive a non-spontaneous chemical reaction (electrolytic cell). The cell potential (EMF) determines the direction and spontaneity of the redox reaction.
Key Components:
- Anode: Where oxidation occurs (loss of electrons)
- Cathode: Where reduction occurs (gain of electrons)
- Salt Bridge: Allows ion flow to maintain charge balance
- Half-Cells: Each electrode with its solution
How to Calculate Cell EMF
The standard cell potential (E°cell) is calculated using the standard electrode potentials:
E°cell = E°cathode - E°anode
Steps:
- Identify the cathode (reduction) and anode (oxidation) half-reactions
- Look up standard reduction potentials (E°) for both half-cells
- Calculate E°cell = E°cathode - E°anode
- If E°cell > 0, the reaction is spontaneous (galvanic cell)
- If E°cell < 0, the reaction is non-spontaneous (electrolytic cell)
When to Use This Calculator
This calculator is useful for:
- Battery Design: Predicting cell voltage and capacity
- Corrosion Studies: Understanding metal oxidation tendencies
- Electroplating: Determining required voltages
- Fuel Cells: Calculating maximum theoretical voltage
- Electrolysis: Finding minimum voltage needed
- Chemical Analysis: Redox titrations and potentiometry
- Research: Predicting reaction spontaneity and equilibrium
Key Formulas
1. Cell EMF
E°cell = E°cathode - E°anode
Standard cell potential from half-cell potentials
2. Gibbs Free Energy
ΔG° = -nFE°cell
Where n = electrons transferred, F = Faraday constant (96,485 C/mol)
3. Equilibrium Constant
K = exp(nFE°cell / RT) = exp(-ΔG° / RT)
Relates cell potential to equilibrium position
4. Nernst Equation
E = E° - (RT/nF) ln Q
Cell potential at non-standard conditions, Q = reaction quotient
5. Spontaneity Criterion
E°cell > 0 → Spontaneous (ΔG° < 0)
Positive cell potential indicates spontaneous reaction
Common Electrochemical Cells
Daniell Cell (Zn-Cu)
Zn|Zn²⁺||Cu²⁺|Cu, E° = 1.10 V. Classic example of galvanic cell.
Lead-Acid Battery
E° ≈ 2.05 V. Used in automobiles, rechargeable.
Lithium-Ion Battery
E° ≈ 3.7 V. High energy density, used in electronics.
Hydrogen Fuel Cell
E° = 1.23 V. Clean energy, water as byproduct.