Non - ideal solutions exhibit either positive or negative deviations from Raoult's law. What are these deviations and why are they caused? Explain with one example for each type.

Explanation

When the vapour pressure of a non-ideal solution is either higher or lower than that predicted by Raoullt's law, the solution exhibits deviations.
These deviations are caused because of unequal intermolecular attractive forces between solute-solvent molecules and solute-solute or solvent-solvent molecules.
Examples of positive deviation: Mixture of ethanol and acetone, carbon- disulphide and acetone.
Examples of negative deviation : Chloroform and acetone, nitric acid and water.