Question

Question #97721

Answer 1

A little more insight is needed.

Raoult's law deals with phase equilibrium between ideal gas phase and an ideal liquid phase.
The condition of equilibrium for any interaction between a component in various phases is that their activity across the phases must be equal.
Assuming a gas and liquid phases are in equilibrium we have
`a^g = a^l`
For ideal gas the activity is equal to the partial pressure of the species. If the gas phase is non-ideal then we can use fugacity in place of partial pressure.

For ideal liquid the activity is the product of its composition and vapor pressure. This can be viewed as pure component fugacity in the liquid phase.

Equating both we get the famous Raoults' law

`y_iP=x_iP_i^(sat)`

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