Question

Preparation of dinitrogen ​

Answer 1

Answer:

In laboratory, dinitrogen is obtained by reacting aqueous solution of ammonium chloride with sodium nitrite. The products obtained consists of impurities such as NO and HNO3 which can be removed by thermal decomposition of ammonium dichromate.

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Answer 2

Answer:

Nitrogen is obtained commercially by liquefaction and fractional distillation of air. This process mainly involves two steps:

Step 1: Air is reduced to liquid air by applying high pressure ranging between 100 and 200 atmospheres. This compressed air is then passed through fine jet where it undergoes expansion. This method is repeated several times which results in the formation of liquid air.

Step 2: The liquid formed undergoes fractional distillation. The boiling point of dinitrogen is lower than that of the liquid oxygen and hence it distils out, leaving behind liquid oxygen. Nitrogen is obtained from the impure liquid.

In laboratory, dinitrogen is obtained by reacting aqueous solution of ammonium chloride with sodium nitrite.

NH4Cl(aq) + NaNO2(aq) → N2(g)+ 2H2O(l) + NaCl(aq)

The products obtained consists of impurities such as NO and HNO3 which can be removed by thermal decomposition of ammonium dichromate. Another method to remove the impurities is to pass the gaseous mixture through sulphuric acid containing potassium dichromate.

(NH4)2Cr2O7  → N2+ 4H2O+ Cr2O3

Decomposition of sodium or barium azide in the presence of high temperature also results in the formation of pure nitrogen.

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