Nitrogen and its inorganic compounds

I.

Introduction
Nitrogen is a chemical with symbol N and atomic number 7. The standard atomic
weight of Nitrogen is 14. At room temperature, it is a transparent, odorless diatomic gas .
Nitrogen forms about 80% of Earth’s atmosphere and is the most abundant uncombined
element. Many industrially important compounds such as: ammonia, nitric acid,
propellant, explosives, cyanides and some types of fertilizers contain nitrogen. Moreover,

Nitrogen is a nonmetal, its electronegativity is 3.04. It is unreactive at standard
temperature and pressure
At atmospheric pressure, molecular nitrogen liquefies and freezes at -210oC. Below
-237.6oC, nitrogen assumes the cubic crystal allotropic form (called the alpha phase). Liquid
nitrogen, a fluid resembling water in appearance, but with 80.8% of the density (the density
of liquid nitrogen at its boiling point is 0.808g/ml), is a common cryogen.
II.

Nitrogen’s properties

In general, nitrogen is un-reactive at standard temperature and pressure because of ít
strong triple bond
1. Reaction with H2: N2 +H2 ⇄ NH3↑ (100oC, high pressure, catalyst: Fe)
2. Reactions with O2
N2 + O2 → NO↑ (>2000oC)
N2 +O2→NO2↑
3. Metal burns in nitrogen
N2 + Al → 2AlN (Aluminium nitride)
N2 +3 Mg → Mg3N2 (Magnesium nitride)
Metal nitrides are hydrolyzed by water
Mg3N2+ H2O → 3Mg(OH)2+2NH3↑
III.

Produce nitrogen (N2)
1. Industry: produced by fractional distillation of liquid air
2. Laboratory
a) Decay some ammonium salts (NH4+) by heat
NH4NO2 → N2↑ + H2O ( to)
NH4Cr2O7 → N2↑ + Cr2O3 + 4H2O ( to)
NH4NO3 → N2↑ + 1/2O2↑ + 2H2O
b) 2NH3 + 3O2 → N2↑ + 6H2O (900oC)
2NH3 + 3CuO → N2 + 3Cu + 3H2O (to)


c) Treat an aqueous solution of ammonium chloride(NH4Cl) with sodium nitrite
(NaNO2): NH4Cl + NaNO2 → N2↑ + NaCl + 2 H2O
IV.

Uses of N2
+) Nitrogen is used to produce ammonia and nitrates are key industrial fertilizers
+) Nutrients for all plants have this element
+)The main use of liquid nitrogen is a refrigerant

A. Ammonia (NH3) and ammonium salts (NH4+)
A.1. Ammonia (NH3)
I. Ammonia is a colorless gas with a characteristic pungent smell
II. Properties
The ammonia molecule has a lone pair electron air, which makes ammonia a base, a
proton acceptor
1. NH3 + H2O ⇄ NH4+ + OH2. NH3’ reactions with acid:
NH3 + HCl → NH4Cl
2NH3 + H2SO4 → (NH4)2SO4

NH3 + HNO3 → NH4NO3
3. NH3’s reactions with metal cations:
Ag+ + 2NH3 → [Ag(NH3)2]+
Cu2+ + 4NH3 → [Cu(NH3)4]2+
Zn2+ + 4NH3 → [Zn(NH3)4]2+
4. Produce Urea ((NH)2CO): 2NH3+ CO2→ H2N─COONH4
H2N─COONH4 → (NH2)2CO (dehydration)
5. NH3’s displacement reactions: displace 1, 2, or 3 H atom by alkali metals
Na + NH3 → NaNH2 + ½ H2↑ (mole fraction: 1:1)
2Na + NH3 → Na2NH + H2↑ (mole fraction: 2:1)
3Na + NH3 → Na3N + 3/2H2↑ (mole fraction: 3:1)
6. Ammonia’s reactions with metal:
2NH3 + 2Al → 2AlN + 3H2↑ (to)
7. Reduction reactions:
N2 + H2

NH3↑ (.100oC,high pressure , catalyst: Fe)

2NH3 + 3O2 → N2↑ + 6H2O (900oC)
4NH3 + 5O2 → 4NO↑ + 6H2O (250oC, catalyst: Pt)
2NH3 + 3Cl2 → N2↑ + 6HCl.
2NH3 + 3CuO → N2↑ + 3Cu↓ + 3H2O (to)
III. Produce ammonia
1. Industry: N2 +H2 ⇄ NH3↑ (100oC, high pressure, catalyst: Fe)
2. Laboratory
a) Treat an aqueous solution of ammonium salts with alkali liquid


NH4Cl + NaOH → NaCl + NH3↑ + H2O
b) Hydrolyze sodium nitride:

Ca3N2 + 6H2O → 3Ca(OH)2 +2 NH3
AlN +3H2O → Al(OH)3↓ + NH3↑
IV.Uses
+) Ammonia is mostly used to produce acid nitric acid, fertilizers
+) People use ammonia to produce hydrazine (N2H4)
+)Solution of NH3 in water is used as a general purpose cleaner for many
surfaces
A.2 . Ammonium salts (NH4+)
I.
Ammonium salts are soluble in water. (NH4+) is hydrolyzed in water
II.
Properties
1. Double displacement reactions:
(NH4)2SO4 + Ba(OH)2 → BaSO4↓ + 2NH3↑ + 2H2O
(NH4)2SO3 + 2HCl → 2NH4Cl + SO2↑ + H2O
NH4Cl + AgNO3 → AgCl↓+ NH4NO3
2. Decay ammonium salts by heat
NH4Cl → NH3↑ + Cl2↑ ( to)
(NH4)2SO4 → 2NH3↑ + H2SO4 ( to)
(NH4)2CO3 → NH3↑ + NH4HCO3 (to)
NH4HCO3 → NH3↑ + CO2↑ + H2O
(Sodium bicarbonate, referred to as ‘baking soda’, is primarily used in
baking)
III.

Produce ammonium salts
Treat NH3 with acid liquids
NH3 + HNO3 → NH4NO3
NH3 + H2SO4 → (NH4)2SO4

IV.

Uses
+) Ammonium salts are used to produce fertilizers, explosives and sodium
bicarbonate (NH4HCO3)
+) Ammonium salts are also used to clean metal surfaces

B. Nitric acid (HNO3)
I.
Nitric acid has a coordinate covalent bond. Oxidation number nitrogen
element in nitric acid is +5
Nitric acid is subject to light decomposition and it’s decayed: 4HNO3 → 4NO2↑ +
O2↑ + 2H2O. The nitrogen dioxide (NO2) remains dissolved in the nitric acid coloring
it yellow.
II. Properties
1. Acidity
Nitric acid is a strong acid: HNO3 + H2O → H3O+ + NO3Reactions with bases, base anhydrides, salts produce nitrate salts
HNO3 + Fe(OH)3 → Fe(NO3)3 + 3H2O
2HNO3 + CuO → Cu(NO3)2 + H2O


2HNO3 + Na2CO3 → NaNO3 + CO2↑ + H2O
2. HNO3 is a strong oxidizing agent because the nitrogen’s oxidation number is
+5 .
Reactions of nitric acid with almost metals (except gold and platinum)
produce metal nitrate salts (M(NO3)n) (n is the highest valence of that metal)
and reducing products of HNO3 (such as NO, NO2, N2O, N2, NH3 or NH4NO3),
depend on nitric acid’s concentration and metal’s reduction)
Fe + 6HNO3 concentrated → Fe(NO3)3 + 3NO2↑ + 3H2O ( to)
3Cu + 8HNO3 dilute → 3Cu(NO3)2 + 2NO↑ + 4 H2O

8Al + 30HNO3 dilute → 8Al(NO3)3+ 3N2O↑+ 15H2O
4Zn+ 10HNO3 very dilute →4Zn(NO3)2+ NH4NO3+ 3H2O
3. Reactions with some nonmetals such as: S, P, C,… produce acidic oxide with
highest oxidation number
S +6HNO3 → H2SO4 + 6NO2↑ + 2H2O
3P + 5HNO3 +2H2O → 3H3PO4 + 5NO↑
C + 4HNO3 → CO2↑ + 4NO2↑ + 2H2O
III.Produce HNO3
1. Industry:
4NH3 + 5O2 → 4NO↑ + 6H2O ( to)
NO + O2 → NO2
3NO2 + H2O → 2HNO3 + NO↑
OR: 4NO2 + O2 + 2H2O → 4HNO3
2. Laboratory
H2SO4 concentrated + KNO3 → KHSO4 + HNO3 (ĐK PƯ: to)
IV. Uses
Nitric acid is mainly for the use of producing TNT, dyes, pharmaceutical products,
ect…

C. Nitrate salts (NO3-)
Every nitrate salt is soluble in water and. The color of this liquid depends on cation Mn+
because ion NO3- is colorless.
I.
Properties of ion NO31. In acidic environment, ion NO3- has the oxidation like nitric acid
3Cu0 + 8H+ + NO3- → 3Cu2+ + 2NO↑ + 4H2O
2. In alkaline environment, ion NO3- is reduced by Be, Zn, Al and NH3 is the
reducing product.
4Zn + KNO3 + 7KOH → 4K2ZnO2 + NH3↑ + 2H2O
8Al + 3NaNO3 + 5NaOH + 2H2O → 8NaAlO2 + 3NH3 ↑
3. Decay nitrate salts by heat

a) Strong metals (K, Na, Ba, Ca)
M(NO3)n → M(NO2)n + n/2O2↑ (to)
b) Medium metals ((Mg, Al, Mn, Zn, Cr, Fe, Ni, Sn, Pb, Cu)


2M(NO3)n → M2On + n/2O2↑ + 2nNO2↑
c) Weak metals (Hg, Ag, Pt, Au)
2M(NO3)n → 2M↓ + n/2O2↑ + 2nNO2↑
II. Uses
+) Nitrate salts are mainly for the use of producing fertilizers such as:
(NH4)2SO4, NH4NO3, (NH2)2CO
+) Potassium nitrate (KNO3) is used to produce gunpowder (contain 75%
KNO3, 10% S và 15% C).
2KNO3 + 3C + S → K2S + N2↑ + 3CO2↑