Explain what is meant by ideal and non-ideal solutions giving suitable examples?

An ideal solution is a solution which has:

1. Thermodynamic properties similar to those of mixture of ideal gases
2. Enthalpy of solution (of mixing) and volume change on mixing is zero, so the Gibb’s free energy is determined by entropy of mixing.
3. Activity coefficients ( which measure deviation from ideal solution ) are equal to one
4. Vapour pressure obeys Raoult’s law.

A non-ideal solution is a solution which does not follow the conditions or rules of ideal solution. Here, the interactions between molecules are similar to the interactions between molecules of different components, i.e. no forces acting between components.

Non-ideal solutions occur:

1. When intermolecular forces between similar molecules are stronger than that present between the solute and solvent molecules.
2.  When intermolecular forces between dissimilar molecules are greater than those between similar molecules.