GROUP V 229
the molecule being linear; in this respect it resembles the isoelec-
tronic molecule of carbon dioxide, O=C=O. There is also a
resemblance in physical properties, but the dinitrogen oxide mole-
cule possesses a small dipole moment, unlike that of carbon dioxide.
Table 9.3
Dinitrogen oxide Oxvgen
Slightly soluble in water (1 vol. in 1 vol. at Almost insoluble
280 K)
No reaction with nitrogen oxide Brown fumes of nitrogen dioxide
Phosphorus burns leaving an equal volume No gas left
of gas (nitrogen)
Diamagnetic* Paramagnetic*
Molecular mass 44 Molecular mass 32
- A few substances such as iron and cobalt-nickel alloys are ferromagnetic i.e. are strongly attracted to the
poles of a magnet. Most other substances are diamagnetic, i.e. are very weakly repelled from the field of a magnet.
Some ions and molecules are, however, paramagnetic, i.e. are very weakly attracted by a magnet. Thus if we hang
a tube containing liquid oxygen (i.e. highly 'concentrated' oxygen) just above the poles of a powerful electro-
magnet, the tube is pulled towards the magnet as shown thus :
U _
N T S
diamagnetism
Paramagnetism implies the presence of single, unpaired, electrons. Hence nitrogen oxide is paramagnetic, and
so is any other molecule or ion containing unpaired electrons. If the total number of electrons in an ion or mole-
cule is odd, then it must be paramagnetic; but some molecules (e.g. Oj and ions have an even number of electrons
and yet are paramagnetic because some of them are unpaired.
It is slightly soluble in water, giving a neutral solution. It is
chemically unreactive and is not easily oxidised or reduced and at
room temperature it does not react with hydrogen, halogens, ozone
or alkali metals. However, it decomposes into its elements on
heating, the decomposition being exothermic:
N 2 O -> N 2 + |O 2 AH * = - 90.4 kJ mor l
Once this reaction has been initiated, it supports the combustion of
many substances since they can burn in the liberated oxygen. In
this respect, it is hardly distinguishable from oxygen itself; but
other properties serve to distinguish the two gases (see Table 9.3).
NITROGEN MONOXIDE (NITRIC OXIDE), NO
Nitrogen monoxide is the most stable of all the oxides of nitrogen.
It can be prepared in small amounts by direct combination of the
