# In the nonideal solution, why can't one of the solute be positive deviation and the other be negative deviation?

In the nonideal solution, why can't one of the solute be positive deviation and the other be negative deviation?
Let's say A and B makes a nonideal solution.
The moleculat force between A and B means A-B.
Let's say A-A > A-B > B-B.
Then A would evaporate more than in the pure state, and B would evaporate less than in the pure state.

• Have you read that it's not possible..? Please refer to any text.. it will be helpful. – ABC Aug 29 '17 at 5:50

For multiple component systems we use activity coefficient $\gamma$ in modified Roult's law as: $$K_i=\gamma \frac{P_i^\star}P$$
and $\gamma$ is defined in the terms of $f$ : fugacity or fictitious pressure for a real gas.