Explain with a suitable diagram and appropriate examples. Why some non-ideal solutions show positive deviation from ideal behavour?

Answer:

In case of positive deviation from Raoult’s law, A-B
interactions are weaker than those between A-A or B-B, i.e., in this case the intermolecular attractive forces between the solute-solvent molecules
are weaker than those between the solute-solute and solvent-solvent molecules. This means that in such solutions, molecules of A (or B) will
find it easier to escape than in pure state. This will increase the vapour pressure and result in positive deviation. Mixtures of ethanol and acetone is good example of this.