Concentration Cell Voltage Calculator
Calculate the voltage of a concentration cell — two identical electrodes with different ion concentrations.
Voltage approaches zero as concentrations equalize.
A concentration cell is a special type of galvanic cell where both electrodes are made of the same material, but the electrolyte concentrations are different on each side.
Because both electrodes are identical, E° = 0.
The voltage comes entirely from the concentration difference, via the Nernst equation:
E = (0.05916/n) × log([high] / [low]) at 25°C
Or more generally:
E = (RT/nF) × ln([high] / [low])
How it works:
- Anode (low concentration side): Metal dissolves → metal ions → solution (oxidation) → M → M^n+ + ne⁻
- Cathode (high concentration side): Metal ions deposit → solid metal (reduction) → M^n+ + ne⁻ → M
- Net result: ions move from high to low concentration until equal → voltage drops to 0
Applications:
- Biological membrane potentials (nerve impulses): Na⁺/K⁺ concentration gradients across cell membranes create voltage (−70 mV for neurons)
- pH meters: glass electrode is essentially a H⁺ concentration cell
- Ion-selective electrodes (ISE): measure specific ion concentrations
- Measurement of activity coefficients in chemistry research
Nernst equation for concentration cell (M^n+ | M):
E = (0.05916/n) × log(C_high/C_low) at 25°C
As C_high → C_low, E → 0. The reaction stops when both sides reach the same concentration.