Chemistry

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Activity Coefficient Calculator.

Calculate an ideal-dilute Debye–Hückel activity coefficient from explicit ionic strength, charge, and A inputs.

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Set your values

Results update as you type.

log₁₀ γ: -0.0509

log₁₀ γ

-0.050900
Activity coefficient: 0.889406

Activity coefficient

0.889406

How to Use

Every model convention and source-dependent parameter is visible. Results update automatically after each edit.

Use Cases

Estimate ion activity in dilute solutions

Useful for chemists and students to quickly estimate how ionic strength and charge affect ion activity in dilute aqueous solutions, aiding in equilibrium calculations.

Example: Calculate the activity coefficient of Ca2+ in a 0.005 M NaCl solution at 25°C (A=0.509).

Teaching and learning electrochemistry

Helps in understanding the Debye–Hückel limiting law and its application in physical chemistry coursework and lab reports.

Example: Compare activity coefficients for monovalent vs divalent ions at the same ionic strength.

Frequently Asked Questions

What is the Debye–Hückel activity coefficient?
It estimates how much a real ion's behavior deviates from ideal due to electrostatic interactions in dilute solutions. It depends on ionic strength, ion charge, and the solvent's temperature-dependent A parameter.
What inputs do I need for this calculator?
You need the ionic strength of the solution (in mol/L), the charge number of the ion (e.g., +1, -2), and the Debye–Hückel constant A (which depends on temperature and solvent). The calculator then applies the limiting law formula.
Is this calculator valid for concentrated solutions?
No, it is designed for ideal-dilute conditions (typically ionic strength < 0.01 M). For higher concentrations, extended Debye–Hückel or specific ion interaction models are needed.

Tips & Common Mistakes

Tips

  • Ensure ionic strength is in mol/L (M) and matches the units of the A parameter (usually (mol/L)^-1/2).
  • Use the correct A value for your temperature and solvent; for water at 25°C, A ≈ 0.509 (mol/L)^-1/2.
  • This calculator is for ideal-dilute solutions; for ionic strengths above 0.01 M, results may be inaccurate.
  • Double-check the ion's charge sign; the coefficient depends on the square of the charge, so sign doesn't matter.

Common Mistakes to Avoid

  • Using molarity of the salt instead of ionic strength, which accounts for all ions in solution.
  • Forgetting to convert concentration units to mol/L before entering ionic strength.
  • Using an A value for a different temperature or solvent without adjusting.

Last updated: August 13, 2026