Electrochemical Cell Potential Calculator – Calculate EMF of Galvanic Cells
Find the standard cell potential (EMF) of galvanic or electrolytic cells using our electrochemical calculator. Enter reduction potentials for cathode and anode to get the cell voltage. Perfect for electrochemistry and physical chemistry students.
Cell potential (EMF) measures the voltage difference between two half-cells in an electrochemical cell. It tells you whether a redox reaction will occur spontaneously.
Cell Potential Formula
Where:
- E°cell = Standard cell potential (volts)
- E°cathode = Standard reduction potential at cathode
- E°anode = Standard reduction potential at anode
Cell Types
| E°cell | Cell Type | Reaction | Example |
|---|---|---|---|
| Positive (+) | Galvanic/Voltaic | Spontaneous | Batteries |
| Negative (-) | Electrolytic | Non-spontaneous | Electroplating |
| Zero (0) | Equilibrium | No net reaction | Dead battery |
Example: Daniell Cell
Cathode: Cu²⁺ + 2e⁻ → Cu (E° = +0.34 V)
Anode: Zn → Zn²⁺ + 2e⁻ (E° = -0.76 V)
E°cell = 0.34 V - (-0.76 V) = 1.10 V (spontaneous)
| Half-Reaction | E° (V) |
|---|---|
| Li⁺ + e⁻ → Li | -3.04 |
| Zn²⁺ + 2e⁻ → Zn | -0.76 |
| Fe²⁺ + 2e⁻ → Fe | -0.44 |
| 2H⁺ + 2e⁻ → H₂ | 0.00 |
| Cu²⁺ + 2e⁻ → Cu | +0.34 |
| Ag⁺ + e⁻ → Ag | +0.80 |
| F₂ + 2e⁻ → 2F⁻ | +2.87 |
Enter values and calculate to see the chart
Step 1: Find the standard reduction potential for the cathode (where reduction occurs).
Step 2: Find the standard reduction potential for the anode (where oxidation occurs).
Step 3: Subtract anode potential from cathode potential to get the cell voltage.
What Is Cell Potential
Cell potential, also called electromotive force (EMF), measures the voltage difference between two electrodes. It tells you whether electrons will flow spontaneously from anode to cathode. Positive voltage means the reaction happens on its own - like in a battery. Negative voltage means you need to supply energy - like in electroplating.
Galvanic vs Electrolytic Cells
The sign of E°cell determines the cell type:
Galvanic (Voltaic) Cells
E°cell > 0. Chemical energy becomes electrical energy. Examples: AA batteries, car batteries, fuel cells. These discharge spontaneously.
Electrolytic Cells
E°cell < 0. Electrical energy drives chemical changes. Examples: electroplating, water splitting, aluminum production. These need external power.
Real-World Applications
Battery designers use cell potential calculations to predict voltage output. Corrosion engineers calculate potentials to understand rust formation. Electroplaters use these values to determine if a coating process will work without external power.
How do you calculate electrochemical cell potential?
Use E°cell = E°cathode - E°anode. Look up standard reduction potentials in a table, then subtract the anode value from the cathode value. For a Daniell cell with Cu²⁺/Cu (0.34V) and Zn²⁺/Zn (-0.76V), you get 0.34 - (-0.76) = 1.10V.
What does a positive cell potential mean?
Positive E°cell means the reaction is spontaneous - electrons flow from anode to cathode without external power. This is how batteries work. Negative E°cell means you need to apply voltage to make the reaction happen, like in electroplating.
Is the anode positive or negative?
In a galvanic cell, the anode is negative (electrons flow out). In an electrolytic cell, the anode is positive (connected to power supply positive). Remember: oxidation always happens at the anode, regardless of cell type.
What affects cell potential?
Temperature, ion concentration, and pressure (for gases) all affect cell potential. The Nernst equation calculates potential under non-standard conditions. Standard potentials assume 25°C, 1M concentrations, and 1 atm pressure.
Why is standard hydrogen electrode potential zero?
The standard hydrogen electrode (SHE) is defined as 0.00V by convention. It serves as the reference point for all other reduction potentials. Think of it like sea level for altitude measurements - arbitrary but useful for comparison.
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