1. From air

• The carbon dioxide in air is removed by concentrated Sodium hydroxide (NaOH) in the flash B.

NaOH(aq)→Na2CO3 (aq)+H2O(l)

• The oxygen in the air is removed by heating copper in the combustion tube.

2Cu(s)+O2 (g)→2CuO(s)

• The copper changes from brown to black because it has been oxidized to Copper II oxide (CuO). The nitrogen (N₂) is collected over water.
• The N₂ obtained is pure. It contains small amount of Argon (rare gases).

2. Reaction of Ammonia (NH₃) and copper II oxide (CuO)

Dry Ammonia (NH₃) is passed over heated copper II oxide. The Ammonia (NH₃) reduces the black copper II oxide to brown copper, water and nitrogen.

2NH3 (g)+3CuO(s)→3Cu(s)+H2O(l)+N2 (g)

The black copper II oxide will change to brown copper. The water condenses in the U-tube.

Physical Properties of Nitrogen

• It is a colorless, odorless gas.
• It is neutral.
• Pure N₂ is slightly lighter than air.
• It is slightly soluble in water.
• It has a very low melting and boiling point.

Chemical Properties of Nitrogen

• It reacts with hydrogen to give Ammonia (NH₃).

N2 (g)+H2 (g)↔2NH3 (g)

• It reacts with magnesium (Mg) and calcium (Ca) to give nitrides.

3Mg(s)+N2 (g)→Mg3N2 (s)

Magnesium nitride reacts with water producing a pungent gas that burns red litmus paper blue (Ammonia).

3Mg3N2 (s)+6H2O→3Mg(OH)2 +3NH3 (g)

• It combines directly with oxygen at about 2000°C to form small amounts of nitrogen II oxide (NO). In nature, this occurs in the atmosphere during lightening flashes.

N2 (g)+O2 (g)→2NO(g)