Question

Which of the following gas dimerises to become stable?

Options

• \[\ce{CO2_{(g)}}\]

• \[\ce{NO2_{(g)}}\]

• \[\ce{SO2_{(g)}}\]

• \[\ce{N2O_{(g)}}\]

Answer 1

\[\ce{NO2_{(g)}}\]

Explanation:

\[\ce{NO2}\] (nitrogen dioxide) dimerises to form \[\ce{N2O4}\] (dinitrogen tetroxide) to become more stable. This occurs because \[\ce{NO2}\] contains an unpaired electron, making it a reactive free radical. By dimerising, it pairs up the unpaired electrons and achieves a more stable structure.

The reaction is \[\ce{2NO2 -> N2O4}\]