Types of Non Ideal Solution

What is non ideal solution ?

Non ideal solution is a solution which does not obey Raoult's law over entire range of concentration. properties of non ideal solution is on mixing, it's enthalpy and volume change. non ideal solution is categorised into two types positive deviation of non ideal solution and negative deviation of non ideal solution.

1. Positive deviation of non ideal solution

When the interaction between (A-B) is weaker than those solute and solvent pure components  (A-A) and (B-B) interation. And due to this vapour pressure is increases which results in non ideal solution showing positive deviation. Examples are Ethanol + Acetone, Benzene + Acetone etc.

2. Negative deviation of non ideal solution

The force of interaction between (A-B) is stronger than those force of interaction between solute and solvent components (A-A) and (B-B). and because of this the vapour pressure decreases which cause non ideal solution showing negative deviation. Example are Phenol + Aniline etc.

Why solution of Trichloromethane and Acetone shows negative deviation ?

In pure Trichloromethane (CHCL3) and pure Acetone (C3H60), there is no Hydrogen bonding but after mixing there is a Hydrogen bonding between Hydrogen of Trichloromethane (CHCL3) and Oxygen of Acetone (C3H60). due to this interaction between the solution molecules become stronger which cause vapour pressure decreases which results in negative deviation.