There are 2 types of non ideal solutions. Here, we will discuss the types of non ideal solutions with the examples.

Types of non ideal solutions

1. Non-ideal solutions showing positive deviation from the expected Raoult’s Law behaviour.
2. Non-ideal solutions showing negative deviation from the expected Raoult’s Law behaviour.

Types of non ideal solutions : Solutions showing positive deviations:

1. The total vapour pressure of the solution is greater than corresponding ideal solution of same composition.
2. This behaviour of solution is described as positive deviation from Raoult’s Law.
3. Boiling points of such solutions are relatively lower as compared to those of pure components. ( vapour pressure is inversely proportional to boiling point )
4. For one intermediate composition, total vapour pressure of the solution is maximum and boiling point is minimum.
5. Such liquid mixture or azeotropes acquires the property of boiling at constant temperature without change in composition.
6. Solutions showing positive deviation from ideal behaviour are called minimum boiling azeotropes.
7. Liquid pairs for which A-B interactions are lower than that of A-A or B-B interactions show this behaviour.
8. For example: cyclohexane enter in to ethanol molecules by breaking its hydrogen bonds.
9. There is a slight increase in volume of solution and absorption of heat.
10. (i) pA > xA PoA , pB > xB PoB , pTotal > xA PoA + xB PoB (ii) ▲Hmix = +ve (iii) ▲Vmix = +ve

Types of non ideal solutions : Solutions showing negative deviations:

1. Liquid pairs for which A-B interactions are higher than that of A-A or B-B interactions show this behaviour.
2. The total vapour pressure of the solution is lesser than corresponding ideal solution of same composition.
3. Solution showing negative deviation from Raoult’s Law shows this behaviour.
4. They are also called as maximum boiling azeotropes.
5. For example CHCl3 forms H-bond with CH3COCH3
6. There is a slight decrease in volume of solution and evolution of heat.
7. (i) pA < xA PoA , pB < xB PoB , pTotal < xA PoA + xB PoB (ii) ▲Hmix = -ve (iii) ▲Vmix = -ve

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