Dealing primarily with changes in colligative properties, it allows for the calculation of molecular weights of dissolved substances and leads to the definition of a solution as ideal.  
It holds only when the molecular attraction between different components is equal to the attraction of any one component in its pure state.  Dealing primarily with changes in colligative properties, it allows for the calculation of molecular weights of dissolved substances and leads to the definition of a solution as ideal.  FTP, identify this law that relates the vapor pressure and mole fraction of a solution, a law named for its French discoverer.
It holds only when the molecular attraction between different components is equal to the attraction of any one component in its pure state.  
Raoult's law