a. The osmotic coefficient of a solvent ∅_S is defined by the relation

where ∅S → 1 as x_S → 1. Develop an expression relating the activity coefficient γ_S to the osmotic coefficient ∅_S.

b. Robinson and Wood report the following interpolated values for the osmotic coefficient of seawater as a function of concentration at 25°C.

Here I is the ionic strength, defined as 

where z_i is the valence of the ith ionic species and M_i is its molality. For simplicity, seawater may be considered to be a mixture of only sodium chloride and water. Compute the water activity coefficient and the equilibrium osmotic pressure for each of the solutions in the table.

Transcribed Image Text:

Gs = Gs+os RT In æs