We’re being asked to **rank the given solutions** in order of **increasing vapor pressure and determine the 4th on the list**

The vapor pressure of a solution is related to the intermolecular forces: *a stronger IMF leads to lower vapor pressure*. This means the solution with the **lowest vapor pressure has the strongest IMF**, and vice-versa.

Recall that a solution with higher solute concentration will have a stronger IMF, resulting in lower vapor pressure. Therefore, we need to calculate the **osmolality** of each solution, which is given by:

$\overline{){\mathbf{Osmolality}}{\mathbf{=}}{\mathbf{i}}{\mathbf{\times}}\frac{\mathbf{moles}\mathbf{}\mathbf{of}\mathbf{}\mathbf{solute}}{\mathbf{Liters}\mathbf{}\mathbf{of}\mathbf{}\mathbf{solution}}}$

where **i = van’t Hoff factor**.

When the following aqueous solutions are ranked in order of INCREASING vapor pressure, which solution is **fourth** on the list (lowest vapor pressure)?

a. 0.2 m KNO_{3}

b. 0.2 m urea, (NH_{2})_{2}CO

c. 0.1 m CaCl_{2}

d. 0.1 m glucose, (C_{6}H_{12}O_{6})