Explain non-ideal solutions and the occurrence of positive and negative deviations in non-ideal solutions.

(N/A) non-ideal solution is one that does not obey Raoult's law over the entire range of concentration.
The vapour pressure of such a solution is either higher or lower than that predicted by Raoult's law. If it is higher,the solution exhibits positive deviation,and if it is lower,it exhibits negative deviation from Raoult's law.
Positive Deviation:
In this case,$A-B$ interactions are weaker than those between $A-A$ or $B-B$. The intermolecular attractive forces between solute-solvent molecules are weaker than those between solute-solute and solvent-solvent molecules. Consequently,molecules of $A$ (or $B$) escape more easily than in the pure state,increasing the vapour pressure.
Example: Mixtures of ethanol and acetone.
Negative Deviation:
In this case,$A-B$ interactions are stronger than those between $A-A$ or $B-B$. The intermolecular attractive forces between solute-solvent molecules are stronger than those between solute-solute and solvent-solvent molecules. This decreases the tendency of molecules to escape,lowering the vapour pressure.
Example: Mixtures of phenol and aniline or chloroform and acetone.