Modern inorganic chemistry

220 GROUP V

Using the apparatus shown in Figure 9.3 it can be shown that

ammonia gas will burn in chlorine gas, the ignition being spon-

taneous in this case:

2NH 3 + 3C1 2 -> N 2 + 6HC1

6HC1 + 6NH 3 -» 6NH 4 C1

If ammonia is used in large excess and the chlorine diluted with

nitrogen, chloramine, NH 2 C1, is formed:

NH 3 + C1 2 -> NH 2 C1 4- HC1

When chlorine gas is in excess a highly explosive substance, nitrogen

trichloride, NC1 3 , is formed:

2NH 3 + 6C1 2 -» 2NC1 3 4- 6HC1

When chlorine is passed into aqueous ammonia, ammonium

chloride and nitrogen are formed. If, however, sodium chlorate(I)

(hypochlorite) is used instead of chlorine, chloramine is first formed:

NH 3 + OC1" -> NH 2 C1 + OH"

Normally the chloramine immediately undergoes further reaction,

giving off nitrogen:

2NH 2 C1 4- OCr + 2OH~ -» N 2 T + 3C1" + 3H 2 O

but in the presence of glue or gelatin the chloramine reacts with

more ammonia to give hydrazine:

NH 2 C1 + NH 3 4- OH" -> N 2 H 4 4- Cl~ + H 2 O

It is thought that the function of the glue or gelatin is to combine

with very slight traces of heavy metal cations, for example Cu^2 + ,

which are known to catalyse the nitrogen-forming reaction.

Ammonia will reduce metallic oxides which are reduced by

hydrogen (for example copper(II) oxide, CuO, lead(II) oxide, PbO),

being itself oxidised to nitrogen:

2NH 3 + 3PbO -> 3Pb + N 2 T 4- 3H 2 O

Reactions with electropositive metals. Ammonia gas reacts with

strongly electropositive metals to form the amide, for example

2Na + 2NH 3 -> 2NaNH 2 + H 2

This reaction also occurs slowly when sodium is dissolved in liquid
ammonia; initially a deep blue solution is formed which then
decomposes giving hydrogen and sodium amide.