The ideal solution R & S is formed when R-S interactions in the solution are similar to the R-R and S-S interactions. It should be of an equal type of component that will interact with itself and the other component. The ideal solution always obeys Raoult’s Law. It is the solution that doesn’t obey Raoult’s Law at all the levels of temperatures and concentrations. It is very much dissimilar from the ideal solution and is referred to as Non- ideal solution.

Characteristics of Non-Ideal Solution

• The interaction between the solute- solute and solvent- solvent is dissimilar from the solute-solvent interaction

• The heat might be released if the enthalpy of mixing is negative, and if the enthalpy of mixing is positive, that means the heat has been absorbed

Examples of Non-ideal Solutions

• Acetone (C₃H₆O) is a highly volatile and colourless liquid, and Carbon disulfide (CS₂) is a colourless and ether-like odour liquid

• Acetone (C₃H₆O) is a highly volatile and colourless liquid, and Benzene (C₆H₆) is an organic chemical compound found in important parts of gasoline and crude oil

• Methyl Alcohol (CH₃OH) is colourless and strong like odour and Water (H₂O) odourless and tasteless liquid at a normal room temperature

Types of Non-Ideal Solutions

Mainly there are two types of non-ideal solutions:

• The positively deviated solution
• The negatively deviated solution

The Positively deviated solution:

In the Positive deviated type of solution, the intermolecular force of attraction between solvent-solute- is less than solvent-solvent and solute-solute interaction. The change in volume of mixing is more than zero. The change in enthalpy of mixing is more than zero.

Examples of the Positively Deviated Solution

• Acetone(C₃H₆O) is a highly volatile and coloured liquid, and Carbon disulfide (CS₂) is a colourless liquid with an ether-like odour

• Acetone(C₃H₆O) is a highly volatile and coloured liquid, and Benzene (C₆H₆) is an organic chemical compound

• Carbon Tetrachloride (CCl₄) is a dense, colourless, highly toxic, volatile, and Chloroform (CHCl₃) is an organic compound

• Methyl Alcohol with the formula (CH₃OH) is a colourless liquid with a strong odour. And Water with the formula (H₂O) is a tasteless and odourless liquid

• Acetone(C₃H₆O) is a highly volatile and coloured liquid, and Ethanol with the formula (C₂H₅OH)  is an organic chemical compound

• Ethanol with the formula (C₂H₅OH)  is a chemical, organic compound and Water with the formula (H₂O) is a tasteless and odourless liquid

The Negatively Deviated solution

In the Negatively deviated solution type of solution, an intermolecular force of attraction between solvent-solute is more than solvent-solvent and solute-solute interaction. The change in volume of mixing is less than zero. The change in enthalpy of mixing is less than zero.

The Examples of Negative Deviated Solutions

• Chloroform (CHCl₃) is an organic compound, and Benzene ( C₆H₆) is an organic chemical compound

• Chloroform (CHCl₃) is an organic compound, and Diether (C₄H₁₀O) compounds with ether linkage consist of two atoms of oxygen

• Acetone(C₃H₆O) is a highly volatile and coloured liquid, and Aniline (C₆H₅NH₂) is also known by the name phenylamine

• Nitric Acid with the formula of (HNO₃) appears as a pale yellow to reddish-brown liquid, and Water with the formula (H₂O) is a tasteless and odourless liquid

• Acetic Acid (C₂H₄O₂) is a colourless and acidic liquid, and Pyridine is highly flammable with the formula of (C₅H₅N)

• Hydrochloric Acid (HCl) is a colourless, strong acid, and Water (H₂O) is a tasteless and odourless liquid

 Ideal and Non-Ideal Solutions Difference

• Ideal solutions obey Raoult’s law, whereas non-ideal solutions do not obey Raoult’s law

• In ideal solutions, between the solvent and solute, the intermolecular interaction is the same as that of the pure components
• Whereas in a non-ideal solution, in between the solvent and solute, the intermolecular interaction is either weaker or stronger than that between the pure compounds

• In an ideal solution, as per the prediction from Raoult’s law, the total vapour pressure is the same
• In a non-ideal solution, the total vapour pressure either increases or decreases from the predicted value by Raoult’s law

• In an ideal solution, the enthalpy of mixing is zero because no heat is either absorbed or released. ΔHmix = 0
• In a non-ideal solution, the enthalpy of mixing is either negative or positive because the heat is either released or absorbed. ΔHmix ≠ 0

• In an ideal solution, the volume of mixing is zero because the sum of the volume of components (solvent and solute) is equal to the total volume. ΔVmix = 0
• Whereas, in a non-ideal solution, there is either expansion or contraction
• That’s why the volume of mixing is not zero.  ΔVmix ≠ 0

• In an ideal solution, by fractional distillation, the components can be separated
• Whereas in a non-ideal solution, by fractional distillation, the components can’t be separated into the pure form

Conclusion

The plot for ideal and non-ideal solutions, so over the whole range of concentration, when a solution obeys Raoult’s law, it is known as the ideal solution. Whereas, over the whole range of concentration, when a solution does not obey Raoult’s law, it is known as a non-ideal solution. The Force of attraction between the solute and solvent is similar to the force of attraction between solvent-solute. It implies that the total vapour pressure over a solution can be related to a mole of the fraction of any one component. Raoult’s Law only works fairly for the ideal solutions. The ideal solution obeys Raoult’s Law, whereas the non-ideal reaction does not obey Raoult’s Law and contains different molecules between the solute and solvent.