An azeotropic mixture of two liquids has a boiling point higher than either of them when it:a)Shows positive deviation from Raoult’s law.b)Shows negative deviation from Raoult’s law.c)Shows ideal behaviour.d)Is saturated.Correct answer is option 'B'. Can you explain this answer?

Question

An azeotropic mixture of two liquids has a boiling point higher than either of them when it:a)Shows positive deviation from Raoult&#8217;s law.b)Shows negative deviation from Raoult&#8217;s law.c)Shows ideal behaviour.d)Is saturated.Correct answer is option 'B'. Can you explain this answer?

Answer

An azeotropic mixture of two liquids has a boiling point higher than either of them when it shows negative deviation from Raoult's law.

Explanation:

Azeotropic mixtures are a special type of liquid mixture that have a constant boiling point and composition. In these mixtures, the vapor phase has the same composition as the liquid phase, which makes it impossible to separate the components by simple distillation.

Raoult's law is a fundamental principle that describes the behavior of ideal mixtures of volatile liquids. According to Raoult's law, the partial pressure of each component in the vapor phase is directly proportional to its mole fraction in the liquid phase.

There are three possible cases for the behavior of a liquid mixture in terms of Raoult's law:

1. Positive deviation from Raoult's law:

In this case, the actual vapor pressure of the mixture is higher than predicted by Raoult's law. This occurs when the intermolecular forces between the components are weaker than the forces between like molecules. The mixture exhibits stronger intermolecular interactions, leading to a lower vapor pressure and a higher boiling point than expected.

2. Negative deviation from Raoult's law:

In this case, the actual vapor pressure of the mixture is lower than predicted by Raoult's law. This occurs when the intermolecular forces between the components are stronger than the forces between like molecules. The mixture exhibits weaker intermolecular interactions, leading to a higher vapor pressure and a lower boiling point than expected.

3. Ideal behavior:

In this case, the mixture follows Raoult's law exactly, and the boiling point of the mixture is determined by the boiling points of the individual components.

So, in the case of an azeotropic mixture with a higher boiling point than either of the components, it must show negative deviation from Raoult's law. This means that the intermolecular forces between the components are stronger than the forces between like molecules. As a result, the vapor pressure of the mixture is lower than expected, leading to a higher boiling point.

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