Activity Coefficient Calculator:
Enter the values of activity, a of a substance and molar concentration, x(mol/L) to determine the value of Activity Coefficient, γ.
Activity Coefficient Formula:
The activity coefficient (denoted as γ) is a measure of the effective concentration of a substance in a mixture, reflecting how the substance behaves in a non-ideal solution compared to an ideal solution. In an ideal solution, the activity coefficient is 1, implying that the substance behaves as it would in a pure state. However, in real solutions, interactions between molecules cause deviations, leading to a different activity coefficient.
The activity coefficient accounts for these deviations and is used in thermodynamics to describe the non-ideal behavior of solutions, particularly in the context of dilute solutions, where it often depends on the concentration of the solute and the solvent. Factors influencing the activity coefficient include temperature, pressure, and the chemical composition of the solution. The concept is essential in calculations of chemical equilibria, colligative properties, and phase diagrams.
In dilute solutions, the activity coefficient is often less than 1, indicating that the solute particles experience attractive interactions with the solvent molecules, reducing their effective concentration. Conversely, a value greater than 1 suggests repulsive interactions between the solute and solvent molecules.
Activity Coefficient, γ is defined as the ratio of the activity, a of a substance to its molar concentration, x(mol/L) in mole per litre.
Activity Coefficient, γ = a / x(mol/L)
γ = activity coefficient.
A = activity of the substance.
x(mol/L) = molar concentration in mole per litre, mol/L.
Activity Coefficient Calculation:
- A solution contains a solute with a molar concentration of 0.5 mol/L and an activity of 0.45. Calculate the activity coefficient γ.
Given: a = 0.45, x(mol/L) = 0.5mol/L.
Activity Coefficient, γ = a / x(mol/L)
γ = 0.45 / 0.5
γ = 0.9.
- Given: a = 2.0, γ = 2.0.
Activity Coefficient, γ = a / x(mol/L)
x(mol/L) = a / γ
x(mol/L) = 2.0 / 2.0
x(mol/L) = 1.0mol/L.