A Model Depicting Why the Vapor Pressure of a Solution of Glucose Is Less Than the Vapor Pressure of Pure Water.
11
Volatile
solvent
(a) Dynamic equilibrium
(b) Glucose added
(c) Dynamic equilibrium
(a)
When water or any volatile solvent is in a closed container, water molecules move into and out of the liguid phase at the same rate in dynamic equilibrium. (b) If a nonvolatile solute such as glucose is. added, some fraction of the surface area is occupied by solvated solute molecules. As a result, the rate at which water molecules evaporate is decreased, although initially their rate of condensation is unchanged. (c) When the glucose solution reaches equilibrium, the concentration of water molecules in the vapor phase, and hence the vapor pressure, is less than that of pure water.
If the ionic compound magnesium chloride, MgCh, is added as a solute to pure water until its concentration is equal to that of glucose in the model shown above,
Choose option a b c or d
a the aqueous magnesium chloride solution will have the same vapor pressure as the aqueous glucose solution.
b the aqueous magnesium chloride solution will have half of the vapor pressure of the aqueous glucose solution.
c the aqueous magnesium chloride solution will have a third of the vapor pressure of the aqueous glucose solution.
d the aqueous magnesium chloride solution will have double of the vapor pressure of the aqueous glucose solution.