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# 1.What is meant by positive deviations from Raoult’s law? Give an example.2.What is the sign of ${\Delta _{mix}}H$ for positive deviation?

Last updated date: 17th Jun 2024
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Hint: Positive deviation indicates that solution no longer behaves as an ideal solution. In general, we can say that, the resultant pressure of solution A-B is more than that of initial pressure of solution i.e. A-A and B-B. Mainly, this deviation is based only on the interactive forces between the particles.

The best example of this deviation is a mixture of ethanol and water. They produce a highly distorted curve with a maximum vapour pressure containing $95\%$ of ethanol by weight.
2.The solute-solvent forces of attraction are weaker than solute-solute and solvent-solvent interaction in case of positive deviation i.e., $A-B < A-A$ or $B-B$ . this corresponds to the enthalpy of mixing which is positive in this case i.e. ${\Delta _{mix}}H > 0$ because the heat absorbed to form new molecular interaction is less than the heat liberated on breaking of original molecular interaction.