Question

Assertion (A) : Hydrogen gas is not evolved when zinc reacts with nitric acid.
Reason (R) : Nitric acid oxidises the hydrogen gas produced to water and itself gets reduced.

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

Answer 1

The Correct Option is A

Step 1: Understanding the Assertion (A):
The assertion states that hydrogen gas is not evolved when zinc reacts with nitric acid. This is true because when zinc reacts with nitric acid, hydrogen gas is not produced. Instead, the reaction forms zinc nitrate (Zn(NO₃)₂) and nitrogen dioxide (NO₂), a brown gas. The reason hydrogen gas is not evolved is that nitric acid is a strong oxidizing agent, which prevents the formation of hydrogen gas.

Step 2: Understanding the Reason (R):
The reason states that nitric acid oxidizes the hydrogen gas produced to water and itself gets reduced. This is true because nitric acid (HNO₃) acts as an oxidizing agent during the reaction. If hydrogen gas were to be produced, it would be oxidized by the nitric acid to form water. Instead, nitric acid itself gets reduced, producing nitrogen oxides (such as NO₂), which are seen as brown gases in the reaction.

Step 3: Analyzing the Correctness of the Answer:
- Assertion (A) is true: Hydrogen gas is indeed not evolved when zinc reacts with nitric acid due to the oxidizing nature of nitric acid.
- Reason (R) is true: Nitric acid oxidizes hydrogen gas (if produced) to water and itself gets reduced to nitrogen oxides. This process is consistent with the absence of hydrogen gas in the reaction.
- Reason (R) is the correct explanation of Assertion (A): The reason directly explains why hydrogen gas is not produced in the reaction, as nitric acid oxidizes any hydrogen gas that might form, preventing its evolution.

Conclusion:
The correct answer is: Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).