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Question
What is meant by negative deviation from Raoult's law? Give an example. What is the sign of ∆mixH for negative deviation?
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Solution
The non-ideal solutions that do not obey Raoult's law over the entire range of concentration and have vapour pressures lower than those predicted by Raoult's law show a negative deviation from Raoult's law.
Example: A mixture of chloroform and acetone
In case of solutions showing negative deviations, ΔmixH has a negative sign.
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