Question

Assertion: Hydrogen gas is not evolved when a metal reacts with nitric acid. Reason:Nitric acid is a strong oxidising agent and it oxidises the H2 produced to water and itself gets reduced to oxides of nitrogen.​

Answer 1

Answer

Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2). But magnesium (Mg) and manganese (Mn) react with very dilute HNO3 to evolve H2 gas.

Assertion and reason are both true and reason is the correct explanation of assertion.

Explanation:

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Answer 2

Hydrogen gas is not evolved when a metal reacts with nitric acid. Nitric acid is a strong oxidising agent and it oxidises the $\[{H_2}\]$ produced to water and itself gets reduced to oxides of nitrogen.​ Both the assertion and reason are correct statements and the reason is the correct explanation of the assertion.

Explanation:

• When a metal reacts with nitric acid, it forms a metal nitrate, oxides of nitrogen and water.

        $\[M + 2HN{O_3} \to MN{O_3} + N{O_2} + {H_2}O\]$      ($M=$ metal)

        $\[M + 4HN{O_3} \to M{(N{O_3})_2} + 2N{O_2} + 2{H_2}O\]$     ($M=$ metal)

• Hydrogen gas is not evolved when metals are treated with nitric acid.
• This is because nitric acid acts as a strong oxidising agent.
• The hydrogen gas which is produced during the reaction is oxidised to water by nitric acid.
• The nitric acid itself gets reduced to oxides to nitrogen.
• Therefore, both the assertion and reason are correct statements and the reason is the correct explanation of the assertion.