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Non-ideal Solutions
Concepts tested here
- Positive deviation from Raoult's law
All Questions
2006 AIPMT-PRE 1 question
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A solution of acetone in ethanol :-In pure ethanol the molecules are held together by strong intermolecular hydrogen bonds.
When acetone is added, its molecules get in between the ethanol molecules and break some of these hydrogen bonds.
The new acetone-ethanol interactions are weaker than the ethanol-ethanol interactions they replace.
Because the intermolecular attractions are weakened, the molecules escape more easily into the vapour phase.
The vapour pressure of the solution is therefore higher than that predicted by Raoult's law, with $\Delta H_{mix} \gt 0$ and $\Delta V_{mix} \gt 0$.
So a solution of acetone in ethanol shows a positive deviation from Raoult's law.