The boiling point of an azeotropic mixture of water and ethyl alcohol is less than that of the theoretical value of water and alcohol mixture. Hence the mixture shows

Options

A. that solution is highly saturated
B. positive deviation from Raoult's law
C. negative deviation from Raoult's law
D. none of these

Answer

To solve the question regarding the boiling point of the azeotropic mixture of water and ethyl alcohol, we can follow these steps:

### Step 1: Understand the Concept of Azeotropes
An azeotropic mixture is a mixture of two or more liquids that has a constant boiling point and composition throughout the boiling process. In this case, we are dealing with an azeotropic mixture of water and ethyl alcohol.

**Hint:** Azeotropes maintain the same composition in both liquid and vapor phases.

### Step 2: Identify the Boiling Points of the Components
The boiling point of pure water is 373 K, and the boiling point of pure ethyl alcohol (C2H5OH) is 351 K.

**Hint:** Knowing the boiling points of the individual components is crucial for understanding the behavior of the mixture.

### Step 3: Analyze the Boiling Point of the Azeotropic Mixture
The boiling point of the azeotropic mixture of water and ethyl alcohol is given as 350.5 K, which is lower than the boiling points of both pure components.

**Hint:** Compare the boiling point of the mixture with those of the individual components to determine the type of deviation from Raoult's law.

### Step 4: Understand the Deviation from Raoult's Law
When the boiling point of a mixture is lower than the boiling points of the individual components, it indicates a positive deviation from Raoult's law. This occurs when the interactions between the different components (solute-solvent) are weaker than the interactions within the same component (solute-solute or solvent-solvent).

**Hint:** Positive deviation means that the vapor pressure of the solution is higher than expected, leading to a lower boiling point.

### Step 5: Conclude the Type of Deviation
Since the azeotropic mixture of water and ethyl alcohol shows a boiling point lower than that of either component, we conclude that it exhibits a positive deviation from Raoult's law.

**Hint:** Remember that positive deviation results in an increased vapor pressure, which lowers the boiling point.

### Final Answer
The correct option is **B: positive deviation from Raoult's law**.