Question

Name a colourless gas liberated on decomposition of nitric acid

Answer 1

Oxygen gas is liberated when nitric acid decomoses.

also NO2 is liberated which is a yellow-  brown coloured gas.

HNO3------> NO2+ O2+ H2O

Answer 2

The decomposition of nitric acid to produce nitrogen dioxide, oxygen and water. This reaction slowly takes place in the concentrated solution, at room temperature, initiated by the absorption of energy in the form of light.

HNO3----> NO2 + H2O +O2

Here, Nitrogen dioxide is a nasty-smelling and deep red-orange gas.

And oxygen gas is a colourless flammable gas

So, answer here is O2 gas