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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.

Concept Fundamentals
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Cell EMF
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ΔG°
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K
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Cell Type
Calculate Cell PotentialSelect half-cells or enter standard potentials

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.
Sources:IUPAC Gold BookNIST Electrochemistry

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

Number of electrons in balanced redox equation
For Nernst equation calculations

Nernst Equation (Optional)

Calculate cell potential at non-standard conditions using concentrations or reaction quotient

Concentration of reduced species
Concentration of oxidized species
Or enter Q directly (overrides concentrations)

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:

  1. Identify the cathode (reduction) and anode (oxidation) half-reactions
  2. Look up standard reduction potentials (E°) for both half-cells
  3. Calculate E°cell = E°cathode - E°anode
  4. If E°cell > 0, the reaction is spontaneous (galvanic cell)
  5. 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.

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