Question

How is the sign of Δ_mixH related to negative deviations from Raoult’s law?

Answer 1

For solutions showing negative deviations from Raoult’s law, `Delta H_"mixing" < 0`. This can be explained as follows:

The energy released during the setup of A-B interaction forces is more than that absorbed while overcoming the A-A or B-B interaction forces because the A-B molecular interaction forces are stronger than the A-A or B-B molecular interaction forces. As a result, the dissolution process is exothermic, and when such a solution forms, a net energy is released. As a result, `Delta H_"mixing"` is negative, meaning that it is less than 0.