Name: Non-ideal Solutions
Uploaded: 2019-07-19
Duration: 8 min 43 s
Description: We know that an ideal solution is a theoretical concept. So, what are non-ideal solutions? Why do they show a deviation from Raoult's law? Let's explore!

Question

How does a non-ideal solution differ from an ideal solution? When does the positive deviations occur from ideality?

Accepted Answer

Ideal solutions : An ideal solution is the solution which obeys Raoult's law perfectly over entire range of concentration and temperature and during its formation there is no change in its enthalpy and volume. Such solutions are formed by mixing the two components which are identical in molecular size, in structure and have almost identical intermolecualr forces.

Examples of ideal solution:- Chlorobenzene and bromobenzene; Benzene and toluene; Ethyl bromide and ethyl iodide.

Non-ideal solutions : Those solutions which do not obey Rault's law are called non-ideal solutions.

Non ideal solutions are formed when the components differ much in their structures and polarities. Non ideal solutions show either positive or negative deviations from Rault's law.

Examples of non-ideal solution :- Ethanol and cyclohexane; Acetone and benzene; Water and methanol.

Positive deviation from Rault's law : This deviation is shown when the forces of attraction between $A - B$ molecules are less than forces of attraction between $A - A$ and $B - B$ molecules in the two liquids forming the solution.

$A$ and $B$ escape easily showing higher vapour pressure than the expected value.

Examples: (i) Ethanol and cyclohexane (ii) Acetone and benzene

How does a non-ideal solution differ from an ideal solution? When does the positive deviations occur from ideality?

Important Questions on Solutions

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