The bolling point of a liguld is defined as the temperature at which its vapor pressure is equal to the external pressure. Explain how the boiling point of a solution of the same liquid containing a nonvolatile solute is higher, and the vapor pressure is lower, than that of the pure substance.
When a nonvolatile solute is added to a liquid, the vapor pressure of the solution decreases. This is because the presence of the solute molecules disrupts the ability of the solvent molecules to escape into the gas phase, thus reducing the overall vapor pressure of the solution.
As a result, the boiling point of the solution is higher than that of the pure solvent. This is because in order for the vapor pressure of the solution to equal the external pressure and reach its boiling point, the solution must be heated to a higher temperature compared to the pure solvent. This higher temperature is required in order to provide enough energy to overcome the reduced vapor pressure caused by the presence of the solute.
In summary, the boiling point of a solution containing a nonvolatile solute is higher than that of the pure solvent because the presence of the solute reduces the vapor pressure of the solution, thereby requiring a higher temperature for the solution to boil.