Question

How to derive the formula of mean activity coefficient

Answer 1

Answer:

Mean activity coefficient:

Activity of a molecule or ion in a solution is referred to as effective concentration. Activity of a molecule or ion depends on

the solvent,  the composition of solution, thus the interaction between solvent and solute components, and the temperature.

Recalling the definition of activity from equilibrium thermodynamics .

$a_{i} =r_{i} \frac{m_{i} }{m_{0} }$

Mean activity coefficient have no unit, but their magnitude depend on the concentration units used. Concentration of the same solution can be given in units mol·kg-1, mol·dm-3, molar fraction