The vapor pressure of a pure liquid changes with temperature as shown by the curve ABC in figure 15.8. There is a sharp break at B where in fact the freezing point curve cameramen .Thus the point correspond to the freezing point of pure solvent. The vapor pressure curve of as solution of a nonvolatile solute in the same solvent is also shown in figure 15.8.It is similar to the vapor pressure curve of the pure solvent and meets the freezing point curve at F indicating that T1 is the freezing point of the solution. the difference of the freezing point of the pure solvent and the solution is referred to as the Depression of freezing point. It is represented by the symbol.
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