Pure water boils at 373 K and pure nitric acid boils at 359 K. The azeotropic mixture of water and nitric acid boils at T.K.

Options

A. `T lt 359 K`
B. `T gt 359 K`
C. `T lt 373 K"but"gt 359 K`
D. Unpredictable

Answer

To solve the problem of determining the boiling point of the azeotropic mixture of water and nitric acid, we can follow these steps:

### Step 1: Understand the boiling points of the pure substances
- Pure water boils at 373 K.
- Pure nitric acid (HNO3) boils at 359 K.

### Step 2: Identify the nature of the solution
- Water and nitric acid form a non-ideal solution, which shows a negative deviation from Raoult's law. This means that the boiling point of the mixture will not be a simple average of the boiling points of the pure components.

### Step 3: Define what an azeotropic mixture is
- An azeotropic mixture is a mixture of two or more liquids that has a constant boiling point and composition throughout the distillation process. In this case, we are looking for a maximum boiling azeotrope.

### Step 4: Determine the composition of the azeotropic mixture
- The azeotropic mixture of water and nitric acid consists of approximately 68% nitric acid and 32% water by mass.

### Step 5: Analyze the boiling point of the azeotropic mixture
- Since the azeotropic mixture has a higher concentration of nitric acid (which has a lower boiling point than water), the boiling point of the azeotropic mixture will be influenced by this composition.
- The boiling point of the azeotropic mixture will be greater than that of pure nitric acid (359 K) because it is a maximum boiling azeotrope.

### Step 6: Compare the boiling points
- The boiling point of the azeotropic mixture will be less than that of pure water (373 K) but greater than that of pure nitric acid (359 K).
- Therefore, we conclude that the boiling point T of the azeotropic mixture is such that:
\[ 359 \, \text{K} < T < 373 \, \text{K} \]

### Conclusion
The boiling point of the azeotropic mixture of water and nitric acid is greater than 359 K and less than 373 K.

### Final Answer:
T is greater than 359 K and less than 373 K.

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