How to Calculate Mean Ionic Activity Coefficient (γ)
Calculate non-ideal solution deviation step-by-step:
Enter Concentration
Input dilute salt concentration C in mol/L (M ≤ 0.1M).
Enter Ion Charges
Input cation charge z+ and anion charge |z-|.
Compute Ionic Strength
Ionic strength I = 0.5 × ∑(c_i × z_i²).
Compute γ & Activity
Apply log10(γ) = -0.509 × |z+ z-| × √I to find effective activity a = γ × C.
Key Features & Physical Electrochemistry
Standard Debye-Hückel Law
Uses standard constant A = 0.509 for water solutions at 298.15 K (25°C).
Ionic Strength Engine
Calculates solution ionic strength I taking multi-valent charge into account.
Effective Chemical Activity
Displays true thermodynamic activity a = γ × C.
Physical Chemistry Guide: Debye-Hückel Limiting Law
In real electrolyte solutions, electrostatic interactions between ions reduce their effective reactivity. The activity coefficient (γ) quantifies this non-ideal behavior:log₁₀(γ) = -A × |z₊ z₋| × √Iwhere A = 0.509 mol⁻¹/² L¹/² at 25°C, z is charge, and I is ionic strength.
Frequently Asked Questions
?Why is the limiting law accurate only below 0.01M - 0.1M?
The limiting law assumes point-charge ions in a continuous solvent dielectric. At higher concentrations, ion sizes and short-range non-electrostatic forces become significant.