Which of the following acids is not used in the preparation of hydrogen from metals?
The correct option is B i.e Nitric acid
Nitric acid, even in its dilute form is not used in the preparation of hydrogen from metals because nitric acid is a powerful oxidising agent. The oxygen formed due to its decomposition, oxidises the hydrogen to give water. Thus, defeating the purpose of reaction.
Example: 3Zn+8HNO3⟶3Zn(NO3)2+4H2O+2NO