Explain the terms ideal and non-idealsolution in the light of forces of interactions operating between molecules in liquid solutions.

Explanation

The solutions which obey Raoult's law over entire range of concentration are known as ideal solutions. For an ideal solution `DeltaV_(mix)=Oand DeltaV_(mix)=O.` The ideal behaviour of the solutions can be explined by considering two components A and B
In pure components, the intermolecular attractive interactions will be of A-A type B-B type, whereas in the binary solution in adition of these two, A-B type of interaction will also be present. If A-A and B-B intermolecular forces are nearly equal to those between A-B this leads to the formation of ideal solution e.g., solution of n-hexane n-heptane
When a solution does not obey-Raoult's law over the entire range of concentration, then it is called non-ideal solution. The vapour pressure of such a solution is either higher or lower, than that predicted by Roult's law.
If is is higher, hte solution exhibits positive deviation and if it is lower it exhibits negative deviation from Raoult's law, in casse of positive deviation, A-B interactions are weaker than those between A-A of B-B i.e., the attractive forces betweeen solute solvent molecules are weaker than those between solute-solute and solvent-solvent molecules e.g., mixture of ethanol and acetone.
For such solutions `" "DeltaH_("mixing")=+ve and DeltaV_("micing")=+ve`
On the other hand in case of negative deviation the intermolecular attractive forces between A-A and B-B are weakeer than those between A-B molecules. Thus, the escaping tendency of A and B types of molecules from the solution becomes less than from the pure liquid i.e., mixture of chloroform and acetone.