Concentration Cell Voltage Calculator

Calculator Inputs

Input basis

Use direct activity if you already corrected for non-ideal behavior.

Label for side A

Label for side B

Side A value

Enter concentration or activity for side A.

Side B value

Enter concentration or activity for side B.

Electrons transferred, n

For Cu²⁺/Cu, use n = 2.

Activity coefficient γ for side A

Activity coefficient γ for side B

Stoichiometric exponent, ν

Keep ν = 1 unless you need a powered activity ratio term.

Temperature

Temperature unit

Decimal precision

Reset

Example Data Table

System	Higher Side	Lower Side	n	Temperature	Approx. Voltage
Cu²⁺/Cu concentration cell	1.000 M	0.010 M	2	25 °C	0.05916 V
Zn²⁺/Zn concentration cell	0.100 M	0.010 M	2	25 °C	0.02958 V
Ag⁺/Ag concentration cell	1.000 M	0.001 M	1	25 °C	0.17748 V

Formula Used

For an identical-electrode concentration cell, the standard potentials cancel, so the driving force comes only from the activity difference between the two half-cells.

Primary equation

E_cell = (RT / nF) ln[(a_high / a_low)^ν]

At 25 °C

E_cell = (0.05916 × ν / n) log₁₀(a_high / a_low)

Where

E_cell = cell voltage in volts
R = gas constant, 8.314462618 J·mol^-1·K^-1
T = absolute temperature in kelvin
n = electrons transferred
F = Faraday constant, 96485.33212 C·mol^-1
a = activity of ionic species
ν = stoichiometric exponent applied to the activity ratio

If you use concentration mode, this page estimates activity with a = γ × C, where γ is the activity coefficient and C is concentration.

How to Use This Calculator

Choose whether your inputs are direct activities or concentrations corrected by activity coefficients.
Enter the two half-cell values and optional custom labels.
Provide activity coefficients when concentration mode is selected.
Enter the number of electrons transferred, n.
Enter ν if your activity ratio must be raised to a stoichiometric power.
Select the temperature value and its unit.
Choose the decimal precision you want in the output table.
Click Calculate Voltage to display the result above the form.
Use the CSV and PDF buttons to export the calculation summary.

FAQs

1) What is a concentration cell?

A concentration cell is an electrochemical cell made from the same electrode pair on both sides. Its voltage comes only from a difference in ion activity or concentration between the half-cells.

2) Why is the standard cell potential not entered?

For an ideal concentration cell with identical electrodes, the standard electrode potentials cancel. That makes the net standard cell potential zero, so only the Nernst concentration term determines the voltage.

3) Should I use concentration or activity?

Activity is more rigorous, especially in non-ideal solutions. Concentration works as an approximation in dilute cases. This calculator supports both, plus activity coefficients for a better correction.

4) What happens when both sides are equal?

If both effective activities are equal, the activity ratio becomes 1. Then ln(1) is zero, so the concentration cell voltage is also zero.

5) Why does temperature affect the result?

The Nernst equation contains absolute temperature. As temperature increases, the concentration-driven contribution grows, so the same activity ratio can produce a larger voltage.

6) Which side becomes the cathode?

For the identical metal-ion case, the side with higher ion activity behaves as the cathode, while the lower-activity side behaves as the anode. This calculator identifies that automatically.

7) What does the stoichiometric exponent ν do?

ν lets you model a powered activity ratio term when your reaction expression needs it. For many standard concentration-cell problems, leaving ν at 1 is appropriate.

8) Can I use this for classroom and lab review?

Yes. It is useful for quick study checks, lab comparisons, and sensitivity analysis. Always verify assumptions, especially solution ideality and the redox form of your half-reaction.