Question

Why dilute nitric acid cannot be used in the preparation of hydrogen?

Answer 1

For this problem, we have to study the action and nature of nitric acid with the hydrogen so that the result which will be obtained will determine the reason for non-participation of nitric acid in the preparation of hydrogen.

Complete step by step solution:
-In the given question, we have to explain the reason for avoiding the use of dilute nitric acid while preparing hydrogen.
-As we know that nitric acid has another name that is aqua fortis which is a highly corrosive acid. The molecular formula of nitric acid consists of one hydrogen, one nitrogen and 3 oxygen molecules.
-Also, nitric acid is also a strong oxidising agent because it can oxidise other molecules by giving an oxygen molecule and reduces itself.
-Now, we know that hydrogen gas consists of two atoms of hydrogen which combine when metal and water react together.
-Metals such as sodium, magnesium, manganese, etc can be used to react with a cheap compound that is water to liberate the hydrogen gas.
-The balanced chemical reaction is:
$2\text{Na + 2}{{\text{H}}_{2}}\text{O }\to \text{ 2NaOH + 2}{{\text{H}}_{2}}$
-But if we use the dilute nitric acid then it will act as an oxidising agent and react with hydrogen gas to produce water molecules.
-As we can see in the chemical reaction:
$\text{2HN}{{\text{O}}_{3}}\text{ + }{{\text{H}}_{2}}\text{ }\to \text{ 2}{{\text{H}}_{2}}\text{O + 2N}{{\text{O}}_{2}}$
Therefore, due to the oxidation of hydrogen gas by dilute nitric acid, nitric acid is not used for
the preparation of hydrogen gas.

Note: Here, metals like magnesium and manganese can produce hydrogen gas when reacted with water but only when the nitric acid is in a more dilute form. Moreover, zinc is also not used for this preparation because it reacts very slowly with an acid.