Vapour pressure of a solvent containing nonvolatile solute is_________.
At any given temperature, the vapor pressure of a solution containing a nonvolatile solute is less than that of the pure solvent. This effect is called vapor pressure lowering. The solid line in Figure is a plot of the vapor pressure of pure water versus temperature. The break in the curve at 0°C is the intersection of the curve of the vapor pressure of the solid with the curve of the vapor pressure of the liquid. The dashed line in is a plot of the vapor pressure of an aqueous solution of sugar versus temperature. Notice that the vapor pressure of the solution is always less than that of the pure solvent.
The vapor pressure of pure water is shown as a solid line; the vapor pressure of an aqueous solution is shown as a dashed line. Note the differences between the solution and the pure substance in melting point and boiling point. |
The surface of a pure solvent is populated only by solvent molecules. Some of these molecules are escaping from the surface, and others are returning to the liquid state. The surface of a solution is populated by two kinds of molecules; some are solvent molecules,