(a) Explain why metals usually do not liberate hydrogen gas with dilute nitric acid.
(b) Name two metals which can, however, liberate hydrogen gas from very dilute nitric acid.

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Solution

(a)Nitric acid $(H N O_{3})$ is a strong oxidising agent.
The Hydrogen gas produced during its reaction with metal gets oxidised to $H_{2} O$ , hence no hydrogen gas is produced.
Instead, it evolves nitric oxides such as $N O_{2}, N O$ etc.

For Eg:

$C u (s) + 4 H N O_{3} (a q) ⟶ C u (N O_{3})_{2} (a q) + 2 N O_{2} (g) + 2 H_{2} O (l)$

(b)Magnesium and Manganese can generate $H_{2}$ with very dilute $H N O_{3}$ because at very low concentration $H N O_{3}$ can not oxidise $H_{2}$ to water

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Similar questions

Why generally Hydrogen gas is not evolved when metals react with dilute Nitric acid?

Correct the following statements :

(a) Hydrogen is used as a fuel for rocket propulsion.

(b) All metals react with acids to give hydrogen.

(d) Very dilute nitric acid reacts with zinc to produce hydrogen.

(e) $C o n c . H_{2} S O_{4}$ reacts with zinc to liberate hydrogen.

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