A solution of two liquids boils at a temperature more than the boiling point of either of them. Hence, the binary solution showsa)negative deviation from raults lawb)positive deviation from raults lawc)no deviation from raults lawd)positive or negative deviation depending on composition.Correct answer is option 'A'. Can you explain this answer?

Question

Answer

Introduction

When two liquids are mixed together to form a binary solution, the boiling point of the resulting solution may be different from the boiling point of either of the pure liquids. This phenomenon is known as deviation from Raoult's law.

Explanation

Raoult's law states that the vapor pressure of a component in a binary solution is directly proportional to its mole fraction in the solution. In other words, the partial pressure of each component in the vapor phase is equal to the product of its mole fraction in the liquid phase and its vapor pressure in the pure state.

However, in some cases, the behavior of a binary solution deviates from Raoult's law. This can occur when the intermolecular forces between the two components of the solution are different from each other and from the pure components.

Negative Deviation from Raoult's Law

In the case where the binary solution boils at a temperature higher than the boiling point of either of the pure components, it indicates a negative deviation from Raoult's law. This means that the actual vapor pressure of the solution is lower than what would be predicted by Raoult's law for that composition.

Explanation of Negative Deviation

When two liquids with different intermolecular forces are mixed together, the molecules of one component may preferentially interact with each other rather than with the molecules of the other component. This results in a decrease in the effective concentration of the molecules in the liquid phase, leading to a lower vapor pressure.

As a result, the solution will have a higher boiling point because it requires more energy to overcome the reduced vapor pressure and reach the boiling point. The stronger intermolecular forces between the molecules of the two components prevent the escape of molecules from the liquid phase, causing the boiling point to be higher.

Conclusion

In summary, when a binary solution boils at a temperature higher than the boiling point of either of the pure components, it indicates a negative deviation from Raoult's law. This occurs due to the preferential interaction of the molecules of one component with each other, resulting in a decrease in vapor pressure and a higher boiling point.

Similar Class 12 Doubts

A binary liquid solution is prepared by mixing n-heptane and ethanol. Which one of the following statements is/are correct regarding the behaviour of the solution?

Binary liquid solutions which exhibit negative deviations from Raoult’s law boil at temperature...than the expected value

24.Assertion: If on mixing the two liquids, the solution becomes hot, it implies that it shows negative deviation from Raoults law. Reason: Solution which show negative deviation are accompanied by decrease in volume.?

If a thin slice of sugar beet is placed in concentrated solution of NaCl then

Top Courses for Class 12

Suggested Free Tests

Related Content

Schools

Competitive Examinations

Quick Access Links

Technical Exams