Lowering of vapour pressure and depression of freezing point

Vapor pressure lowering is a colligative property of solutions. Thevapor pressure of a pure solvent is greater than the vapor pressure of a solution containing a non volatile liquid. This lowered vapor pressureleads to boiling point elevation.

Method 2 Finding Vapor Pressure with Dissolved Solutions

1.Write Raoult's Law.
2.Identify the solvent and solute in your solution.
3.Find the temperature of the solution.
4.Find the solvent's vapor pressure.
5.Find the mole fraction of your solvent.
6.Solve 

Freezing-point depression is the process in which adding a solute to a solvent decreases the freezing point of the solvent. Examples include salt in water, alcohol in water, or the mixing of two solids such as impurities in a finely powdered drug. In the last case, the added compound is the solute, and the original solid is thought of as the solvent. The resulting solution or solid–solid mixture has a lower freezing point than the pure solvent or solid. This phenomenon is what causes sea water, (a mixture of salt [and other things] in water) to remain liquid at temperatures below 0 °C (32 °F), the freezing point of pure water.

Calculate :

Step 1: Calculate the freezing point depression of benzene. T_f = (Freezing point of pure solvent) - (Freezing point of solution)

Step 2 : Calculate the molal concentration of the solution. molality = moles of solute / kg of solvent.

Step 3: Calculate K_f of the solution. T_f = (K_f) (m)