The non ideal solution showing positive deviation :

Explanation

In these solutions, magnitude of forces of interaction decreases on mixing the two components of the solution. A ------B interactions are less than that of A ------A and B-----B interactions.
So, partial vapour pressure of each component and total pressure of solution will be greater as compared to an ideal solution. `p_(A)gtp_(A)^(@)x_(A),p_(B)gtp_(B)^(@)x_(B)`. In the given figure dotted lines represent the behaviour of the two components present in the ideal solution. Behaviour of non-ideal solution is indicated by normal lines. These solutions have following characteristics :
(i) `DeltaV_("mixing")` is +ve. This is due to hte fact forces of attraction decreases and hence volume of solution increases.
(ii) `DeltaH_("mixing")` is +ve. The process of mixing is endothermic. Energy is needed to form the solution. For solid solute, solubility increases with increase in temperature.
Examples of solutions : a) Ethyl alcohol and water. b) Acetone and ethyl alcohol.