Question

Nitric acid is not used in the preparation of hydrogen.

Answer 1

Nitric acid (HNO₃) is a strong oxidising agent.

Oxidizing Agent: This is a type of substance that itself gets reduced and oxidises another substance present in the reaction.

• It will reduce itself and oxidise the other substance in the reaction. So, nitric acid is not used in the preparation of hydrogen.

Reason: Nitric acid being a strong oxidizing agent will oxidize the hydrogen formed in the reaction and will result in the formation of water.

For example:

• When Zinc (Zn) reacts with hydrochloric acid (HCl) acid it results in the production of hydrogen gas and zinc chloride.

Zn (s) + HCl (aq) $\to$ ZnCl₂ (s) + H₂ (g)

• But when Zinc (Zn) reacts with nitric acid (HNO₃) it does not form hydrogen gas. It forms water (H₂O), nitrogen dioxide (NO₂), and zinc nitrate (Zn(NO₃)₂).

As hydrogen forms in the reaction between zinc (Zn) and nitric acid (HNO₃) will get oxidised because of the strong oxidising nature of nitric acid.

Zn (s) + 4HNO₃ (l) $\to$ Zn(NO₃)₂ + 2NO₂ (g) + 2H₂O (l)