An ideal solution or ideal mixture is a solution in which the enthalpy of solution is zero ΔHsolution = 0; the closer to zero the enthalpy of solution, the more "ideal" the behavior of the solution becomes. An ideal mixture is one in which the activity coefficients are equal to one. The concept of an ideal solution is fundamental to chemical thermodynamics and its applications, such as the use of colligative properties. Since the enthalpy of mixing (solution) is zero, the change in Gibbs free energy on mixing is determined solely by the entropy of mixing.
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