Why mixture of ethanol and acetone show positive deviation to roults law?

Question

Answer

Positive Deviation from Raoult's Law in Ethanol-Acetone Mixture

Introduction

Raoult's law states that the vapor pressure of a solution is directly proportional to the mole fraction of each component present in the solution. This law is valid for ideal solutions, where the interactions between the molecules of the components are similar. However, in real solutions, the interactions between the molecules are not always the same, leading to deviations from Raoult's law.

Explanation

In the case of ethanol and acetone mixture, the interactions between the molecules are not similar. Ethanol has a polar hydroxyl group, while acetone has a polar carbonyl group. These two functional groups have different polarities and sizes, leading to different interactions between the molecules.

The positive deviation from Raoult's law occurs when the vapor pressure of the solution is higher than the expected value based on Raoult's law. In the case of ethanol and acetone mixture, the positive deviation occurs because the interactions between the molecules are weaker than expected.

Due to the weaker interactions between the molecules, the solvent molecules can escape more easily from the solution, leading to a higher vapor pressure than expected. This phenomenon is also known as the azeotropic point, where the composition of the vapor is the same as that of the liquid.

Conclusion

The positive deviation from Raoult's law in the ethanol and acetone mixture occurs due to the difference in the polarity and size of the functional groups present in the molecules. This deviation leads to weaker interactions between the molecules, leading to a higher vapor pressure than expected.

Answer

A solution of acetone in ethanol shows positive deviation from Raoult's Law due to miscibility  of these two liquids with the difference of polarity and length of hydrocarbon chain(breaking of H-Bonding between the molecules of ethanol)..

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