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.

Chemical Reactions and Equations

Chemical Properties of Acids

Options

(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.

Official Answer

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

Nitric acidOxidizing agentHydrogen gasWaterReduction

Marking Scheme

11 mark for selecting the correct option (a).

Hint

Recall the special property of Nitric acid as an oxidizing agent compared to $HCl$ or $H_2SO_4$ .

Quick Oral Answer

Hydrogen gas is not evolved with nitric acid because $HNO_3$ is a strong oxidizing agent that converts the produced $H_2$ into $H_2O$ .

Analysis & Explanation

In Activity 1.3 of the text, we observe that metals like Zinc ( $Zn$ ) react with dilute sulphuric acid ( $H_2SO_4$ ) to evolve hydrogen gas ( $H_2$ ). However, Nitric acid ( $HNO_3$ ) is a very strong oxidizing agent.

Assertion (A) is true: When $Zn$ reacts with $HNO_3$ , $H_2$ gas is not evolved.
Reason (R) is true: $HNO_3$ oxidizes the $H_2$ produced into water ( $H_2O$ ) and itself gets reduced to nitrogen oxides like $NO_2$ , $NO$ , or $N_2O$ .

Since the oxidizing nature of the acid explains why the gas is converted to water, Reason (R) is the correct explanation for Assertion (A).

Common Mistakes

1Assuming all acids react with metals to produce hydrogen gas.
2Not realizing that $HNO_3$ acts as an oxidant rather than just an acid in this context.

Interesting Facts

Very dilute nitric acid (1%) can actually react with Magnesium ( $Mg$ ) and Manganese ( $Mn$ ) to evolve hydrogen gas, as its oxidizing power is significantly reduced at that concentration.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 1 mark in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Chemical Properties of Acids" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2024 paper.