Preparation of Nitrogen Gas (N2) in Laboratory
78% of atmosphere is covered by nitrogen gas. Gaseous nitrogen is not a reactive compound in room conditions. Nitrogen gas is prepared in laboratory scale and industrial scale for specific purposes. In this tutorial, we will discuss how to prepare Nitrogen gas in the laboratory in detail.
Content
- Why preparation of nitrogen gas is important?
- Preparation methods and reactions of nitrogen gas in the laboratory
- Combustion of ammonia in the air or oxygen gas
- Ammonia gas and Copper oxide heating reaction
- Heating Ammonium nitrite (NH4NO2)
- Heating Potassium dichromate (K2Cr2O7)
- Heating Sodium Azide (NaN3)
- Silver oxide and ammonia gas reaction
- Ammonia and bleaching powder reaction
- Ammonia and nitric oxide reaction
- Preparation of nitrogen gas In the Industry
- Preparation of nitrogen gas using air | Liquid air distillation
- How to separate nitrogen gas from oxygen gas?
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Why preparation of nitrogen gas is important?
Liquid nitrogen
Liquid nitrogen is used as a coolant. Liquid nitrogen only exist between -2100C - -1960C. So you can see temperature of liquid nitrogen is very low.
Gaseous nitrogen
Gaseous nitrogen is used as a filling agent in food industry because its reactivity characteristics are poor. There are more uses of nitrogen gases and they are explained in detail below.
Preparation methods and reactions of nitrogen gas in the laboratory
There are several methodologies to prepare Nitrogen gas in the laboratory according to the availability of chemicals. Each those reactions with required other physical parameters are explained in detail here.
Combustion of ammonia in the air or oxygen gas
When ammonia is combusted in the air or oxygen, nitrogen gas and water are given as products.
2NH3 + 5O2 → N2 + 3H2O
Ammonia is oxidized to nitrogen gas while oxygen gas is reduced. Chemical balanced equation of the respective reaction is mentioned above. Oxidation number of nitrogen atom in ammonia molecule is oxidized from -3 to 0.
Ammonia gas and copper oxide heating reaction
Send ammonia gas through a hot copper oxide layer. Ammonia will oxidized to nitrogen gas and copper oxide is reduced to copper metal. Furthermore water vapor is given as other product. You can observe the colour change of solid particles during the reaction. Copper oxide is black colour and produced copper is red colour.
NH3 + CuO → N2 + Cu + H2O
Heating Ammonium nitrite
In this reaction, only one chemical is used to prepare nitrogen gas. Nitrogen gas and water vapor are given as products. Nitrogen atoms are at two different oxidation states at Ammonium nitrite. Because Ammonium nitrite can be found or easily prepared in the laboratory, this method is much convenient to use in your laboratory.
- -3 is the oxidation number of nitrogen in ammonium cation and it is oxidized to 0.
- +3 is the oxidation number of nitrogen in nitrite ion and it is reduced to 0.
NH4NO2 → N2 + H2O
Heating Ammonium chloride with Potassium dichromate
Heat orange colour Potassium dichromate ( K2Cr2O7) with ammonium chloride. Nitrogen gas, chromium oxide ( Cr2O3 ), Potassium chloride (KCl) and water are given as products. Chromium oxide is green colour. Usually both Ammonium chloride and Potassium dichromate are available in the laboratory, this method is also a easy to apply in the laboratory to prepare nitrogen gas.
K2Cr2O7 + 2NH4Cl → N2 + Cr2O3 + 2KCl + 4H2O
As well, you can heat ammonium dichromate ((NH4)2Cr2O7) alone to prepare nitrogen gas.
(NH4)2Cr2O7 → N2 + Cr2O3 + 4H2O
- Chromium atom is reduced from +6 to +3.
- Nitrogen atom is oxidized to -3 to 0.
Heating Sodium Azide (NaN3)
When sodium azide has enough heat supply, it decomposes to sodium and nitrogen gas. This reaction is used in safety air bags in vehicles and detonator.
2NaN3 → 2Na + 3N2
Silver oxide and ammonia gas reaction | Ag2O + NH3 = Ag + N2 + H2O
This is another reaction to prepare nitrogen gas. When heat is available, silver oxide decomposes to silver metal and oxygen gas because Silver oxide (Ag2O) is not stable to heat. Then produced oxygen gas will reacts with ammonia to give nitrogen gas as explained earlier in this tutorial.
2Ag2O → 4Ag + O2
Can I obtain nitrogen gas, by heating copper oxide with ammonia gas?
Copper oxide (CuO) is stable to heat. It does not decompose to metal and oxygen gas when heat. Therefore, ammonia does not react with zinc oxide.
Ammonia and bleaching powder reaction
A redox reaction reaction occurs. Active part of bleaching powder is hypochlorite anion (OCl-). Nitrogen gas, calcium chloride and water are products.
2NH3 + 3CaOCl2 = N2 + 3CaCl2 + 3H2O
Ammonia and nitric oxide reaction
Nitric oxide is reduced to nitrogen and ammonia is oxidized. As products nitrogen gas and water vapor are given.
6NO + 4NH3 = 5N2 + 6H2O
Summary of Reactions of Nitrogen gas preparing in the laboratory
Can I prepare nitrogen gas by the reaction of ammonia gas and zinc oxide when heat is supplied?
No. Zinc oxide does not give oxygen gas when heating (Zinc oxide does not decompose). So due to no oxygen gas, ammonia does not react and nitrogen gas is not given as a result.
Preparation of nitrogen gas In the Industry
Preparation of nitrogen gas using air | Liquid air distillation
Air is cooled and pressurized to liquidize. Then liquid air distillate to separate nitrogen.
How to separate nitrogen gas from oxygen gas?
Send produced gas to a magnesium metal piece and give some heat to occur the reaction (when temperature is high, it increses the reaction rate). We know alkali earth metals react with both oxygen and nitrogen gases and give metal nitrides and metal oxides.
After some time, reacted metal piece is added to the water. Both magnesium oxide and magnesium nitride will give two precipitates.
But in one solution, a gas (ammonia gas) is emitted. Then, you can indicate ammonia gas by ammonia gas testing reactions or experiments. So now, you can separate oxygen gas from nitrogen gas.
Questions
Why nitrogen gas is used in packaging goods?
Nitrogen gas is not reactive and at ordinary conditions and does not react with goods inside packages.
Why sodium nitrite and ammonium chloride mixture will give nitrogen gas when heat is supplied?
When both compounds are mixed, it gives ammonium cations and nitrite anions. When ammonium cations and nitrite anions are together and get heat, nitrogen gas emits.
NOTE
Do not mix sodium nitrate. It will give nitrous oxide (N2O) instead of nitrogen gas.
why is copper mixed with oxygen in the preparation of nitrogen?
When ammonia is heated with oxygen in thee presence of copper, nitric oxide (NO) is given. Copper is behaved as a catalyst in this reaction.
Heat + Cu (as a catalyst) + 4NH3 + 5O2 = 4NO + 6H2O
But, when ammonia gas is heated with CuO, ammonia is reduced to nitrogen gas.
2NH3 + 3CuO = N2 + 3Cu + 3H2O
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