1. Brown: Nitrogen dioxide (NO2) gas often exhibits a brown or reddish-brown colour. It is a major air pollutant and can contribute to smog and cause respiratory problems.
2. Colourless: Nitric oxide (NO) gas is colourless. It is an important signalling molecule in biological systems but can be toxic in high concentrations.
3. Reddish-orange: Dinitrogen tetroxide (N2O4) gas has a reddish-orange colour. It is a toxic and corrosive gas used in rocket propulsion and as an oxidizer in certain chemical reactions.
4. Yellowish-brown: Nitrogen trioxide (NO3) gas appears as a yellowish-brown gas. It is a highly reactive and unstable compound that can decompose explosively.
5. White or Grey: Nitrogen pentoxide (N2O5) can appear as a white or grey solid or gas. It is a strong oxidizing agent and can react violently with water.
It's important to note that the colour of nitrogen oxide gases can vary depending on factors such as temperature, pressure, and concentration. Additionally, some nitrogen oxide gases may exist as colourless gases under certain conditions but can exhibit colour changes when they react with other substances or undergo chemical transformations.
