Question

Hydrogen gas is not evolved when metals react with a compound X. Identify X

Answer 1

A metal is an element with metallic bonds and the ability to form positive ions (cations). Metals are often represented as a cloud of delocalized electrons surrounded by a lattice of positive ions. Hydrogen is a colourless, odourless, tasteless diatomic gas with the chemical formula H₂. It is non-toxic, nonmetallic, and highly combustible.

Complete answer:
A metal is an element with metallic bonds and the ability to form positive ions (cations). Metals are often represented as a cloud of delocalized electrons surrounded by a lattice of positive ions. Hydrogen is a colourless, odourless, tasteless diatomic gas with the chemical formula H₂. It is non-toxic, nonmetallic, and highly combustible.
Since nitric acid is a good oxidising agent, it oxidises the hydrogen to create water, no hydrogen gas is produced when a metal reacts with it. It reduces itself to any of the nitrogen oxides (N₂O, NO, NO₂) after oxidizing the H₂ released to water.
Magnesium (Mg) and manganese (Mn), on the other hand, create H₂ gas as they react with very dilute HNO₃.
An oxidising agent (oxidant, oxidizer) or oxidising agent (oxidiser) is a compound that has the ability to oxidise other compounds (accept their electrons) in chemistry.

Note:
An oxidising agent (oxidant, oxidizer) or oxidising agent (oxidiser) is a compound that has the ability to oxidise other compounds (accept their electrons) in chemistry.
Since nitric acid is a good oxidising agent, it oxidises the hydrogen to create water, no hydrogen gas is produced when a metal reacts with it. It reduces itself to any of the nitrogen oxides (N₂O, NO, NO₂) after oxidizing the H₂ released to water.