Question

Give reasons for the following :
(i) NO (Nitric oxide) is paramagnetic in the gaseous state but diamagnetic in the liquid and solid states. Why ?
(ii) Nitric oxide becomes brown when released in air.

Answer 1

(i) NO has an odd number of electrons (7+8=15 electrons) and hence is paramagetic in the gaseous state. But in liquid and solid states, it exists as a dimer (Table 11.14, page 11//19) and hence is diamagnetic in these states.
(ii) Nitric oxide has one unpaired electron and hence is very reactive.
As a result, it readily combies with `O_(2)` of the air to form nitrogen dioxide `(NO_(2))` which has brown colour.
`underset("Colourles")(2NO)+O_(2)tounderset("Brown")(2NO_(2))`