Which of the following oxides of nitrogen is coloured?

Due to $p\pi - p\pi$ bonding interactions, nitrogen forms $N_2$ but phosphorus forms $X$ and does not form a diatomic molecule. Identify $X$.

Which of the following is the most suitable drying agent for ammonia gas?

The element that can form multiple bonds with itself from the following is

Ammonia gas is dried by using ...........

Which of the following is a colorless solid?