Answer:
Raoult's law is not a good approximation when the compound is very dilute in the liquid phase.
Step-by-step explanation:
Thermodynamics defines ideal mixture as a mixture in which all the molecules of the different species involved are so similar between each other that intermolecular forces between different molecules are the same to those of similar molecules. Thus, Raoult's law takes this definition and stablish that when a compound is highly concentrated in the solution behaves as if it is in a pure solution.
Also, the Raoult's law stablish that the partial pressure (
) of every component in an ideal mixture of liquids is equal to the pressure of the pure component (
) multiplicated by the molar fraction in the solution of that component (
)
The answer "When the compound has a high mole fraction in the liquid phase" is wrong because this is the case that follows the Raoult's law. And the answer "When the compound has a high mole fraction in the vapor phase." talks about the fraction in the vapor, and Raoult's law use the molar fraction in the solution.