Question

Rank the following list of aqueous solutions and solvents according to decreasing vapor pressure. The substance with the highest vapor pressure should be placed on top.
pure water, 0.050 M urea, 0.10 M glucose, 0.20 M sucrose

Answer 1

0.050 M Urea, 0.10 M glucose, 0.20 M sucrose and pure water.

Explanation:

Vapor pressure is the measure of pressure existing above the surface of the solution. Depending upon the vapor pressure of solutions, the boiling points will differ. In other words, decrease in vapor pressure leads to increase in the boiling point.

Since, the number of molecules present above the surface of the solution leads to easy evaporation of those molecules. But if the number of molecules on the surface or vapor pressure on the surface will be less, the boiling point will increase.

Thus, 0.050 M urea has the highest vapor pressure indicating that it can be easily evaporated, then 0.10 M of glucose has the vapor pressure followed by 0.20 M sucrose. Finally, the vapor pressure of water is the lowest and it will have the boiling point of 100 degree celsius.