Question

Write two differences between ideal and non-ideal solutions.

Answer 1

Hint:One of the crucial differences between ideal and non-ideal solutions is the extent of their obedience of Raoult’s law. With this in mind, try to distinguish between these two types of solutions.

Complete step by step answer:
The fundamental difference between an ideal and non-ideal solution is the application of Raoult’s law. So let us first understand what it is.
The law states that, the vapour pressure of a solution containing a non-volatile solute at a particular temperature is equal to the vapour pressure of pure solute at that particular temperature multiplied by the mole fraction of the solvent. Mathematically this can be represented as follows:
\[{{P}_{solution}}=P{}^\circ \times {{\chi }_{solvent}}\]
Here:
- ${{P}_{solution}}$ is the vapour pressure of the solution.
- $P{}^\circ $ is the vapour pressure of pure solvent.
- ${{\chi }_{solvent}}$ is the mole fraction of the solvent. The formula for the same is :-
\[{{\chi }_{solvent}}=\dfrac{Moles\text{ of solvent}}{Total\text{ moles in the solution}}\]

Now, as we have covered the basics we can move on to the differences between ideal and non-ideal solution.

Ideal solution	Non-ideal solution
1. It obeys Raoult’s law to the furthest extent possible.	1. Does not obey Raoult’s law.
2. The molecular attractions between solute and solvent particles are the same as that between solvent-solvent particles.	2. The molecular attraction is different between solute-solvent particles and that between solvent-solvent particles.
3. The proportion of solvent particles that change into their vapour forms remains unchanged even when solute particles are added.4. The liquid and vapour form of the solvent always remain in a dynamic equilibrium.	3. The vapour pressure of solvent significantly decreases when solute particles are added to the solvent.4. The equilibrium is quite disturbed because of the various forces of nature at play.
5. As more and more solute particles are added to the solution, there is a gradual decrease in vapour pressure, which if plotted in a graph gives a straight line.	5. The decrease in vapour pressure is not in a linear manner.
6. Ideal solutions can be converted into non-ideal solutions when the solute particles of different dimensions are put together in the solution.	6. Non-ideal solutions approach the properties of the ideal solutions when they are in extremely diluted conditions.
7. When two ideal solutions are mixed, there is no change in enthalpy or volume of the solution.	7. When two non-ideal solutions are mixed, the change in volume and enthalpy is very significant.
8. For example solutions of benzene-toluene, n hexane- n heptane and ethyl bromide-ethyl iodide.	8. For example solutions of sugar-water, alkane and kerosene etc.

Note:
Ideal solutions do not exist in practicality. This is because there are many factors that do not allow the solutions to behave ideally. Such as for a solution to be perfectly ideal, the size of the solute and solvent particles should be exactly equal; but this can only happen in real circumstances when both solute and solvent are the same compound chemically. But then that is not a solution.