Chemistry
Activity Coefficient Calculator
Estimate the activity coefficient of an ion in a dilute solution using the Debye-Hückel limiting law.
Your inputs
Change any value to update the result instantly.
Activity coefficient (γ)
0.9636
log₁₀ γ
-0.0161
Effective activity (γ × c)
0.001 mol/L
Deviation from ideal behaviour
3.638 %
Model validity
Within the limiting-law range (I ≤ 0.001 mol/kg)
The limiting law is a dilute-solution approximation. A = 0.509 applies to water at 25 °C only.
What this calculator does
Estimates the activity coefficient of an ion in a dilute electrolyte solution with the Debye-Huckel limiting law.
What your result means
A value below 1 shows how much the ion behaves as if it were less concentrated than it really is, because of electrostatic shielding by surrounding ions.
Formula and working
log₁₀ γ = −A z² √I
- 1
Collect the inputs
Charge on the ion (z) = 1; Ionic strength (I) = 0.001 mol/kg; Solvent constant (A) = 0.509; Molar concentration of the ion (optional) = 0.001 mol/L
- 2
Apply the formula
log₁₀ γ = −A z² √I
- 3
Result
Activity coefficient (γ) = 0.9636
Frequently asked questions
Symbols and assumptions
- gamma
- Activity coefficient
- A
- Solvent constant, 0.509 for water at 25 C
- z
- Charge number of the ion
- I
- Ionic strength in mol/kg
- • Ions are point charges in a uniform dielectric.
- • A = 0.509 applies to water at 25 C.
- • Ionic strength is on a molal basis.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • The limiting law is only reliable up to about I = 0.001 mol/kg. Above that use the extended Debye-Huckel or Davies equation.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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