Preparation of Nitrogen Gas, Physical Properties, Compounds

78% of atmosphere is covered by nitrogen Gas. Gaseous nitrogen is not reactive in room conditions. Nitrogen forms a lot of compounds with other elements such as ammonia, different oxides, nitric acid. Nitrogen is used in domestic and chemical industrial purposes.


Nitrogen molecule | N2 molecule

In this lesson, we learn followings of nitrogen gas.

  • Occurrence of nitrogen element and gas
  • Preparation of nitrogen gas from different reactions
  • Physical characteristics


Occurrence of nitrogen element and gas



Preparation of nitrogen gas

There are several ways to produce nitrogen gas in laboratory scale and industrial scale. All reactions of nitrogen preparing in the laboratory is explained below.



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.



Ammonia gas and copper oxide heating reaction | NH3 + CuO = N2 + Cu + H2O

Send ammonia gas to the hot copper oxide. Ammonia will oxidized to nitrogen gas and copper oxide is reduced to copper metal. Furthermore water vapor is given as other product. Copper oxide is black colour and produced copper is red colour.



Heating Ammonium nitrite | NH4NO2 +HEAT

Nitrogen and water vapor gives as the products. Nitrogen atoms are at two different oxidation states at Ammonium cation and nitrite anion.

  • -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.


From potassium dichromate by heating | K2Cr2O7 = N2 + Cr2O3 + H2O

Heat orange colour potassium dichrmoate ( K2Cr2O7). Nitrogen gas, chromium oxide ( Cr2O3 ), and water are given. Chromium oxide is green colour.

  • Chromium atom is reduced from +6 to +3.
  • Nitrogen atom is oxidized to -3 to 0.


Sodium Azide | NaN3 + HEAT

When sodium azide has enough heat, it decomposes to sodium and nitrogen gas. This reaction is used in air bags in vehicles and detonator.



Combustion of Ammonia with Oxygen or Air | NH3 + O2 = N2 + H2O

You can burn ammonia gas in the presence of oxygen gas or air. However, ammonia gas reacts with oxygen gas to give nitrogen gas and water vapor.



Silver oxide and ammonia 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. Then produced oxygen gas will reacts with ammonia to give nitrogen gas.



Ammonia and bleaching powder reaction | NH3 + Ca(OCl)2 = N2 + CaCl2 + H2O

A redox reaction reaction occurs. Active part of bleaching powder is hypochlorite anion (OCl-). Nitrogen gas, calcium hypochlorite and water are products.



Ammonia and nitric oxide reaction | NO + NH3 = N2 + H2O

Nitric oxide is reduced to nitrogen and ammonia is oxidized. As products nitrogen gas and water vapor are given.



All Reactions of Nitrogen Gas Preparing

nitrogen gas producing reactions

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.



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.



Physical properties of N2



Chemical properties of N2 gas

  • Main Component in air (volume ratio - 79%)
  • Inactive in room temperature
  • Reacts with oxygen gas in high temperatures and gives nitric oxide (NO) gas and nitrogen dioxide (NO2)


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.



Reactivity of Nitrogen gas

nitrogen diatomic molecule

N2 is a very inactive element. A very strong triple bond (946 kJmol-) is the reason for this inactivity of N2.


  • N is less active. But not completely inactive. N2 react with O2 under lightnings to give nitric oxide (NO).
  • N2 can react with with H2 in the presence of catalyst to produce NH3.
  • Nitrogen does not react with alkali metals except lithium. Lithium gives lithium nitride with N2.
  • N2 react with Mg to produce Mg3N2


How atmospheric nitrogen becomes soluble compounds in water?


HNO3 and HNO2

  • NO is formed by the reaction of N2 and O2 in lightnings. Produced NO reacts with again to give NO2. These NO2 reacts with water vapor producing HNO3 and HNO2.
  • In automobile engines, NO and NO2 are formed by N2 and O2. These NO2 and NO reacts with water vapour producing HNO3 and HNO2.
  • Nitric oxide (NO) is a neutral oxide and nitrogen dioxide (NO2) is a an acidic gas. NO2 dissolves in the rain and forms nitric acid.

Uses of Nitrogen Gas

  • Nitrogen is a raw material of Haber process. Haber process is the industrial ammonia production method. Nitrogen gas reacts with Hydrogen gas to produce ammonia.


Questions Asked by Students


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.



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