Solution 'A' contains acetone dissolved in chloroform and solution 'B' contains acetone dissolved in carbon disulphide. The type of deviations from Raoult's law shown by solutions A and B, respectively are:
Non ideal solutions showing positive deviation :
The intermolecular attractive forces between solute-solvent molecules are weaker than those between solute-solute and solvent-solvent molecules i.e.
A-B < A-A and B-B interactions.
Acetone has some hydrogen bonding which is disrupted by carbon disulphide when they are mixed - this shows a positive deviation from ideality.
Non ideal solutions showing negative deviation :
The intermolecular attractive forces between solute-solvent molecules are stronger than those between solute-solute and solvent-solvent molecules i.e.
A-B > A-A and B-B interactions
A mixture of chloroform and acetone forms a solution with negative deviation from Raoult's law. This is because chloroform molecules are able to form hydrogen bonds with acetone molecules. This decreases the escaping tendency of molecules for each component and consequently the vapour pressure decreases resulting in a negative deviation from Raoult's law.