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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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