Total number of acidic oxides among $N_2O_3, NO_2, N_2O, Cl_2O_7, SO_2, CO, CaO, Na_2O$ and $NO$ is $...........$

Pure $HNO_3$ is a colorless liquid,but it turns light brown in the presence of light. This is due to its decomposition into which of the following substances in small amounts?

Which of the following molecules contains the highest number of $P-H$ bonds?

What happens when iron is treated with concentrated nitric acid $(HNO_3)$?

Enlist the main uses of nitrogen.

Which oxide of nitrogen is a coloured gas?