Vapor pressure represents a state of dynamic equilibrium in which the rate of liquid escaping to gas is equal to the rate of gas condensing to liquid. Liquids with stronger intermolecular forces have a smaller amount of liquid escaping to gas, and thus have a lower vapor pressure.

Diethyl ether does not create hydrogen bonds, whereas water does. Even though diethyl ether has a greater molecular weight, it will have weaker intermolecular forces. The hydrogen bonding interactions in water will cause molecules to "stick," preventing them from converting to the gas phase and lowering the overall vapor pressure of water. Diethyl ether has a higher vapor pressure than water due to the intermolecular forces of the two compounds.

Raoult's law can be written as .

When the formation of a solution has a positive enthalpy, it is considered to be endothermic. An endothermic reaction will result in the solution's vapor pressure being higher than predicted by Raoult's law. This is because an endothermic reaction results in weaker intermolecular bonds, which increases the vapor pressure.

A volatile solute will contribute to the vapor pressure found in the container. As a result, we have to use Raoult's law, which takes this solute's vapor pressure into consideration.

Raoult's law is written as , where P is the partial pressure for each component and X is the mole fraction of each component.

We must include the vapor pressures of both the solute and the solvent in order to find the percentage composition of the solute in the solution. Since there are only two compounds contributing to vapor pressure in the solution, we can designate the mole fraction of the solute as X and the mole fraction of the solvent as (1-X). Doing this, the equation can be filled in, as below.

 or 67.5% solute in the container.

Since both liquids are volatile, they will both contribute to the solution's vapor pressure. Their impact will be based on their individual vapor pressures, as well as the molar fraction for which each liquid is responsible. This gives us Raoult's law:

Each  represents the liquid vapor pressure, and each  represents the corresponding molar fraction of that particular liquid. Since we have an equimolar mixture, each liquid accounts for 50% of the solution, or in this case 0.5.

This would result in a solution vapor pressure of 172.5 mmHg if conditions were ideal. However, since the reaction is exothermic, stronger bonds are formed in the solution, and the vapor pressure will be lower than expected.

The boiling point is defined as the temperature at which the vapor pressure above the solution equals the atmospheric pressure. Recall that vapor pressure is also a colligative property. The vapor pressure decreases as solutes are added. This means that more energy, in the form of heat, is required to increase the amount of molecules escaping the solution and, subsequently, increase the vapor pressure to that of the atmospheric pressure. This increased demand of energy results in an increased boiling point.

Vapor pressure change is calculated using the following equation.

where  is change in vapor pressure,  is mole fraction of solute, and  is vapor pressure above pure solvent. First, let’s calculate the mole fraction.

The vapor pressure of pure solvent is . Recall that there are  in ; therefore, the vapor pressure of pure solvent is . We can now solve for the change in vapor pressure.

This means that the vapor pressure decreased by  after the addition of glucose.

Note that vapor pressure also depends on the amount of ions.

where  the number of ions. Glucose does not dissolve into ions; therefore, . If we were given another molecule, such as , then we will have to set  and calculate  accordingly.