There are two types of liquid solutions : (I) Ideal solution and (II) Non-ideal solution.I. Ideal solution : A solution which obeys Raoult’s law of vapour pressure is called an ideal solution.
In these solutions, intermolecular forces between A-A and B-B molecules are same as thatof between A and B.
ΔH ‌mixing=0;ΔV ‌mixing=0
Examples :
(i) Benzene + toluene
(ii) n-Hexane + n-heptane
(iii) Chlorobenzene + bromobenzene
(iv) Ethyl bromide + ethyl iodide
II. Non-ideal solution : Asolution which does not obey Raoult’s law of vapour pressure is called non-ideal solution. They are of two types. (a) Non-ideal solution with negative deviation: When intermolecular forces between A and B are stronger than between A-A and B-B, then intermolecular force increases, volume decreases, vapour pressuredecreases and heat is released.
Hence, ΔV=−ve,ΔH=− ve,ΔP=− ve
This is why, the solution is known as non-ideal solution with –ve deviation.
$P_{A}Examples :
(i) Chloroform + acetone
(ii) Water + sulphuric acid
(iii) HCl + water
(iv) Acetone + aniline

(b) Non-ideal solution with positive deviation:When intermolecular forces between A and B are weaker than that of A-A and B-B.
In this case intermolecular force decreases, volume increases, vapour pressure increases, enthalpy increases.
ΔV=+ ve,ΔH=+ ve,ΔP=+ ve
So, it is called non-ideal solution with positive deviation.
PA>xA P0A,PB>xB P0B and PS>xA P0A+xB P0B
Examples :
(i) Ethanol + water
(ii) Chloroform + ethanol