Читать книгу Geochemistry - William M. White - Страница 101

How does chemical potential vary in an ideal solution? Consider the vapor pressure of a gas. The derivative of G with respect to pressure at constant temperature is volume:

Written in terms of partial molar quantities:

If the gas is ideal, then:

(3.24)

and if we integrate from P° to P we obtain:

(3.25)

where μ^P° is the chemical potential of the pure gas at the reference (standard state) pressure P°. This is the standard-state chemical potential and is written as μ°. If we let P° be the vapor pressure of pure i and P be the vapor pressure of i in an ideal solution, then we may substitute X for P/P° into Raoult's law (eqn. 3.8) to obtain the following:

(3.26)

This equation describes the relationship between the chemical potential of component i and its mole fraction in an ideal solution.