Non-Ideal Solution
A solution that departs from Raoult's law because interactions between unlike molecules differ from those between like molecules.
Formula / equation
p ≠ x p°
Unit
Pa
In depth
Non-ideality produces a measurable enthalpy and volume change on mixing and shows as a curved vapour-pressure composition plot. Where the curve departs far enough to produce a maximum or minimum, the mixture forms an azeotrope that cannot be separated by simple distillation.
Examples in the real world
Ethanol with water shows positive deviation; nitric acid with water shows negative deviation.