Explain the following properties of hydrides of nitrogen :
(i) Thermal stability
(ii) Reducing power
(iii) Boiling point
Answers
Explanation:
ANSWER
(i) Name and formula Name Formula
(1) Nitrogen: Ammonia Nitric Acid NH
3
HNO
3
(2) Phosphorous: Phosphine PH
3
(ii) Basic property: Ammonium is a mono basic anhydride that dissolves in water in in form of NH
4
OH (ammonium) hydroxide.
Ammonium hydroxide is a base. Hence, it has a more basic nature. Nitric acid is also a strong mono-basic acid which ionized in water and form of H
3
O
+
and NNO
3
−
ions.
Hence, it has also more basic nature. Phosphene combine with halogen acids in gaseous state and forms phosphonium. There phosphonium halides decompoe as soon as possible and reform phospone.
PH
3
+HX→
Phosphonium halide
PH
4
X
[X = Cl, Br or I]
PH
4
X
H
2
O
PH
3
−H+X
Hence it has more acidic property due to formation of H
+
and it has also more basic nature.
Therefore, it is clear that hydrides of Nitrogen and Nitrogen family has more basic nature.
(ii) Reducing property: Ammonia gas is a strong reducing agent. It reduces hot metallic oxides into metals.
Nitric acid is a strong oxidant i.e. reducing agent, as it easily decomposes to produce nascent oxyen.
2HNO
3
→H
2
O+2NO
2
+
Nitrogen di-oxide
[O]
On passing phosphene gas into the solutions of copper silver and mercury salts metal phosphides are precipitated.
3CuSO
4
+2PH
3
→Cu
3
P
2
+3H
2
SO
4
3HgNO
3
+PH
3
→Ag
3
P+3HNO
3Hence, it has strong reducing property.
Therefore, from the above reasons and explanation it is clear that hydrogen of nitrogen family have strong reducing property.
(iv) Bond angle Ammonia: (ref. image)
Bond angle is 107.3
o.
(v) Melting and boiling points: Melting point (except for Sb and Bi) and boiling point increase on going down the group from N to B. This is because, electropositive and metallic character increase and hence binding energy of atomic crystal also increases