Question

The gas dissolved in nitric acid which gives pale yellow colour

Answer 1

Sulphur is that gas giving pale yellow colour when dissolved in nitric acid

Answer 2

According to Le Chatelier's Principle, the equilibrium proceeds backward to compensate the decrease in P N O 2 and thus more N O 2 gas is released. The gas flows quickly along with the bubbled gas and this prevents the forward reaction. This seems like quite a roundabout method but it works