5. It is used to manufacture ammonia.
5. Liquid nitrogen is used to cool materials to very low temperature.
5. Used in the manufacture of fertilizers.

Oxides of Nitrogen

The two most important oxides of nitrogen are;

5. Nitrogen dioxide (NO₂) and

5. Nitrogen monoxide (NO).

Preparation of Nitrogen dioxide (NO₂)

It can be prepared in the laboratory by heating lead nitrate crystal

PbNO3 (s)→PbO(s)+2NO2 (g)+O2 (g)

Properties of Nitrogen dioxide (NO₂)

• It is a brown gas.
• It is an acidic gas.

Preparation of Nitrogen Monoxide (NO)

It is prepared in the laboratory by reacting 50% of nitric acid (HNO₃) and copper.

Cu(s)+HNO3 (aq)→Cu(NO3)2 (aq)+H2O(l)+NO(g)

Properties of Nitrogen Monoxide (NO)

• It is a colorless gas but turns brown when exposed to air due to the oxidation of the NO to NO₂.
• It is a neutral gas.

AMMONIA (NH₃)

It is a covalent molecule with a trigonal shape and has a bond angle of 107°C.

Laboratory Preparation of Ammonia (NH₃)

It is prepared in the laboratory by heating Ammonia salt and NaOH or Ca(OH)₂.

2NH4Cu(s)+NaOH(aq)→NH3 (g)+NaCu(s)+2H2O(l)

The ammonia is dried using calcium oxide and man of air because it is lighter than air.

NB: Concentrated sulphuric acid (H₂SO₄) and anhydrous calcium chloride (CaCl₂) cannot be used to dry ammonia because they will react.

NH3 (g)+H2SO4 (aq)→NH4)2SO4 (aq)

The product here is a complex compound.

That is H₂SO₄ absorbs ammonia.

Physical Properties of Ammonia (NH₃)

• It is a colorless gas with a pungent and choking smell.
• It is very soluble in water.
• It has a very low and can easily be liquid.
• It is lighter than air.
• It turns moist red litmus paper blue. It is the only alkaline gas.

Remember: Only ammonium sulphate (NH₄SO₄) can be used instead of ammonium chloride (NH₄Cl).

Ca(OH)2 (aq)+NH4SO4 (aq)→CaSO4 (aq)+2H2O(l)+2NH3 (g)

2NaOH(aq)+NH4SO4 (aq)→Na2SO4 (aq)+2H2O(l)+2NH3 (g)

Chemical Properties of Ammonia (NH₃)

• Ammonia reacts with hydrogen chloride gas (HCL) to produce white fumes of Ammonium chloride (NH₄Cl). This is the test for Ammonia (NH3).

NH3 (g)+HCL(g)→NH4Cl(s)

• Ammonia (NH₃) is a reducing agent; it reduces black copper II oxide to brown copper.

2NH3 (g)+CuO(s)→Cu(s)+3H2O(l)+N2 (g)

• It dissolves in water to form an alkaline solution.

NH3 (g)+H2O(l)→NH4OH(g)

Uses of Ammonia (NH₃)

• It is used to manufacture Nitric acid (HNO₃).
• It is used to manufacture ammonium fertilizers. Eg: Ammonium sulphate and ammonium phosphate.
• It is used as a refrigerant or high latent heat of vaporization because it has a very low boiling point and can be liquefied easily.
• It is used in laundry because it solvent hard water and can remove oil and grease from materials.

Test for Ammonia (NH₃)

Has an acidic choking smell. Its smell is due to the fact that gas temporarily paralyses the respire system muscles. In large quantities it causes asphyxiation. It turns moist red litmus paper blue.