Stoichiometry
According to Raoult's law, "The vapor pressure exerted by component in a solution is proportional to the mole fraction of that component." Raoult's law is not applicable under the following assumption/condition.
No component is concentrated at the surface of the solution
The component molecules are non polar and are of almost equal size
In the formation of solution, chemical combination/molecular association between unlike molecules takes place
The attractive forces between like and unlike molecules are almost equal
EXAMIANS