Question

Which among the following oxides of nitrogen is a brown coloured gas?

• A. \(\mathrm{N_2O_5}\)
• B. \(\mathrm{N_2O_3}\)
• C. \(\mathrm{NO_2}\)
• D. \(\mathrm{N_2O_4}\)

Hint:

Brown fumes observed in reactions involving nitrogen oxides usually indicate the presence of \(\mathrm{NO_2}\).

Answer 1

The Correct Option is C

Step 1: Recall physical properties of nitrogen oxides.
Different oxides of nitrogen have characteristic colours depending on their electronic structure and molecular association.

Step 2: Analyse each oxide.
\(\mathrm{N_2O_5}\) is a colourless solid.
\(\mathrm{N_2O_3}\) is deep blue in liquid state.
\(\mathrm{NO_2}\) is a brown coloured toxic gas.
\(\mathrm{N_2O_4}\) is colourless due to dimerisation of \(\mathrm{NO_2}\).

Step 3: Conclusion.
Nitrogen dioxide (\(\mathrm{NO_2}\)) is the brown coloured gas.