Question

Consider the following:
Assertion (A): Nitric acid - water mixture is a maximum boiling azeotrope.
Reason (R): Nitric acid - water mixture shows positive deviation from Raoult’s law.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct, but (R) is not correct
• D. (A) is not correct, but (R) is correct

Hint:

Maximum boiling azeotropes usually exhibit negative deviation from Raoult's law due to stronger intermolecular forces between components. Always correlate boiling point behavior with Raoult’s law deviations.

Answer 1

The Correct Option is C

Step 1: Understand the assertion (A)
A mixture of nitric acid and water forms a maximum boiling azeotrope. This means it has a constant boiling point and behaves as a single substance during phase change. This statement is correct. Step 2: Understand the reason (R)
A positive deviation from Raoult's law occurs when the interactions between unlike molecules (HNO$_3$ and H$_2$O) are weaker than those between like molecules, leading to increased vapor pressure and lower boiling point. However, nitric acid-water mixture forms a maximum boiling azeotrope, which generally corresponds to a negative deviation (stronger interactions, reduced vapor pressure, and higher boiling point). Step 3: Analyze the correctness of each statement
\begin{itemize} \item Assertion (A): Correct – nitric acid-water mixture does form a maximum boiling azeotrope. \item Reason (R): Incorrect – it shows negative deviation from Raoult’s law, not positive. \end{itemize} Conclusion: (A) is correct, but (R) is not correct.