Vapor Pressure and Raoults Law

The lowering of the vapor pressure of a solvent due to the presence of nonvolatile, nonionizing solutes is summarized by Raoult s Law. 

The vapor pressure of a solvent in an ideal solution is directly proportional to the mole fraction of the solvent in the solution. 

Now solvent + - soiute = 1, SO 1 — solvent = solute- We cau express the hwering of the vapor pressure in terms of the mole fraction of the solute. 

Solutions that obey this relationship exactly are called ideal solutions. The vapor pressures of many solutions, however, do not behave ideally. 

EXAMPLE 14-4 Vapor Pressure of a Solution of Nonvolatile Solute 

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