The p-Block Elements

Dinitrogen

Do you know what those chips packet have in them? Yes! A lot of air and some chips! Isn’t it? However, that is not air! That is nitrogen! Yes! But, why do we use dinitrogen there? In this chapter, we will look at dinitrogen, its compounds and uses.

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What is Dinitrogen?

Dinitrogen constitutes almost 78% of the earth’s atmosphere. It is the most available element present in the air. It is the seventh most abundant uncombined element found in the universe. Scottish physician Daniel Rutherford discovered dinitrogen back in the year 1772. The symbol of this chemical element is N and its atomic number is 7.

Dinitrogen

Preparation of Dinitrogen

We can obtain nitrogen commercially by liquefaction and fractional distillation of air. This process mainly involves two steps:

Step 1

We have to reduce air to liquid air by applying high pressure between 100 to 200 atmospheres. After this, we pass this compressed air through a fine jet where it undergoes expansion. We repeat this method 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. We obtain nitrogen from the impure liquid. In a laboratory, we obtain dinitrogen by reacting an 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 HNO3which can be removed by thermal decomposition of ammonium dichromate. Another method in which we can remove the impurities is by passing the gaseous mixture through sulphuric acid that has potassium dichromate in it.

(NH4)2Cr2O → N2+ 4H2O+ Cr2O3

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

Physical Properties of Dinitrogen

Now, we look at the physical properties of dinitrogen.

  • Nitrogen is a colourless, odourless and diamagnetic in nature.
  • It is a non-toxic gas.
  • It is sparingly soluble in water.
  • Nitrogen undergoes condensation to form a colourless liquid. This, on solidification results in the formation of snow like mass.

Chemical Properties of Dinitrogen

1) Dinitrogen has a high bond enthalpy due to the N = N bond. Due to this, it is inert at room temperature. However, the reactivity increases as the temperature increases. At high temperatures, nitrogen molecules react with metals. This reaction results in the formation of respective ionic nitrides. The molecules react with non-metals to form covalent nitrides.

6Li +N2heat →  2Li3N                 

2) At about 773 K, it reacts with hydrogen to form ammonia in Haber’s Process.

N2(g) + 3H2(g) 773k 2NH3(g)                 

3) Nitric oxide is formed by the reaction of nitrogen molecule with the oxygen molecule at a temperature of 2000 K.

N2(g) + O2(g)2NO(g)

Solved Example for You

Q: Give some uses of dinitrogen.

Ans: It is mainly used in the industrial manufacturing of compounds such as ammonia, calcium cyanamide etc. Dinitrogen is used in the manufacturing industries such as iron and steel to obtain an inert atmosphere. We use liquid nitrogen in food industries as a preservative and as a refrigerant.

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