Nitrogen is a very important part of our atmosphere. It forms 78% of our atmosphere by volume and 75% by mass.
Preparation : We have two types of productions of Nitrogen:
Commercial production : The commercial production of Nitrogen is done by the liquifaction and fractional distillation of air.
Lab production : In lab Nitrogen can be produced by several methods-
I. When aqueous solution of ammonium chloride is treated with sodium nitrite.
NH4Cl(aq)+NaNO2(aq)→ N2(g) + 2H2O(l) + NaCl(aq)
II. Dinitrogen can also be obtained by the thermal decomposition of ammonium dicromate.
(NH4)2Cr2O7 →N2(g) + 2H2O(l) + Cr2O3
III. Thermal decomposition of sodium or barium azide also gives dinitrogen. Nitrogen obtained by this method is very pure.
Ba(N3)2 → Ba + 3N2
Ammonia was detected by Priestley in 1774. It is generally formed by the bacterial decomposition of nitrogenous matter found in plants and animals. We can find it in a very less amount in air and soil.
Commercial production: Ammonia is produced by Haber’s process commercially. In this process we prepare a setup with following optimum conditions:
1. Pressure :200 × 105 Pa or 200 atm(Approx), 2. Temperature : About 700 K & 3. Catalyst : Iron oxide with small amount of K2O & Al2O3.
Under these conditions ammonia is produced by the reaction : N2(g) + 3H2(g) → 2NH3(g)
The catalyst is used to increase the production rate of NH3.
III. Oxides of Nitrogen
Nitrogen reacts with oxygen to form different oxides with different oxidation state
1. N2O -Dinitrogen Oxide or Nitrous Oxide or Laughing Gas:
Oxidation state of Nitrogen: 1
Preparation: It can be produced by heating ammonium nitrate.
NH4NO3 N2O + 2H2O
Properties : 1. Nitrous oxide is a colourless gas.
2. It is a has with sweet taste and pleasant odour.
3. It can create laughter when inhaling in a sufficient amount due to which it is called laughing gas.
4. It is soluble in cold water but not in hot water.
5. Nitrous oxide is heavier than air.
Uses : 1. As propellant, 2. As anaesthetic in minor surgical operations with oxygen
II. HNO3-Nitric Acid
Commercial Preparation(Ostwald Process):
The mixture of ammonia and air when passed over platinum gauze catalyst at 7500C-9000C, then ammonia is oxidised to nitric acid.
4NH3+5O2 – 4NO + 6H2O
By oxidising, the nitric oxide is converted to nitrogen dioxide.
2NO + O2 – 2 NO2
When nitrogen dioxide is cooled and absorbed in water, nitric acid is obtained.
3NO2 + H2O – 2HNO3 + NO
Lab Preparation: In the laboratory, nitric acid is formed by heating the mixture of KNO3 or NaNO3 and concentrated H2SO4 in a glass retort.
KNO3 + H2SO4 – KHSO4 + HNO3
NaNO3 + H2SO4 – NaHSO4 + HNO3