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Question
How is the sign of ΔmixH related to positive deviations from Raoult’s law?
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Solution
For solutions showing positive deviation from Raoult’s law, `Delta H_"mixing" > 0`. This can be explained as follows:
More energy is needed to overcome A-A or B-B interaction forces than is released during the setup of A-B interaction forces during solution formation because the A-B molecular interaction forces are weaker than the A-A or B-B interaction forces. Heat is thus absorbed during the creation of such a solution, and the dissolution process is endothermic. For this reason, `Delta H_"mixing"` is advantageous in this instance.
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