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NCERT Class XII Chemistry
Chapter - The p-Block Elements
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Question : 5
Total: 74
How is nitrogen prepared in the laboratory? Write the chemical equations of the reactions involved.
Solution:  
In the laboratory, dinitrogen is prepared by treating an aqueoussolution of ammonium chloride with sodium nitrite.
NH4Cl(aq)+NaNO2(aq)→ N2(g)+2H2O(l)+NaCl(aq)
Small amounts of NO and HNO3 are also formed in this reaction. Theseimpurities can be removed by passing the gas through aqueous sulphuricacid containing potassium dichromate. It can also be obtained by thethermal decomposition of ammonium dichromate.
(NH4 )2Cr2O7
Heat
–––––––▶
N2+4H2O+ Cr2 O3
Very pure nitrogen can be obtained by the thermal decomposition ofsodium or barium azide.
Ba (N3 )2
‌Heat
–––––––▶
Ba+3N2
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