Mean Ionic Activity Coefficient (γ±) Calculator
This calculator computes the mean ionic activity coefficient (γ±) for 1:1, 1:2, 2:1, and 2:2 electrolytes using the Debye–Hückel extended equation (valid up to I ≈ 0.1 M).
log γ± = – (0.51 |z₊ z₋| √I) / (1 + √I) (for 25°C in water)
Note: 1:2 means |z₊|=1, |z₋|=2 (e.g., Na₂SO₄); 2:1 means |z₊|=2, |z₋|=1 (e.g., CaCl₂)
Mean Ionic Activity Coefficient (γ±) =
Activity (a±) for 0.1 m molality ≈
Activity (a±) for 0.1 m molality ≈
About the Calculation
The Debye–Hückel limiting law extended form used here is:
log₁₀ γ± = –0.51 × |z⁺ z⁻| × √I / (1 + √I)
(A = 0.51 for water at 25°C)
This approximation is reasonably accurate for dilute solutions (I ≤ 0.1 M).
For higher concentrations, more advanced models (Pitzer, etc.) are needed.