Describe the methods of preparation,properties,and uses of dinitrogen gas $(N_2)$.

(N/A) Methods of preparation of dinitrogen $(N_2)$:
$1$. Commercial preparation: Dinitrogen is produced by the liquefaction and fractional distillation of air. Liquid nitrogen $(bp = 77.2 \ K)$ distills out first,leaving behind liquid oxygen $(bp = 90 \ K)$.
$2$. Laboratory preparation: It is prepared by treating an aqueous solution of ammonium chloride $(NH_4Cl)$ with sodium nitrite $(NaNO_2)$.
$NH_4Cl(aq) + NaNO_2(aq) \rightarrow N_2(g) + 2H_2O(l) + NaCl(aq)$.
Small amounts of $NO$ and $HNO_3$ are formed as impurities,which are removed by passing the gas through aqueous sulfuric acid containing potassium dichromate $(K_2Cr_2O_7)$.
$3$. Thermal decomposition: Pure dinitrogen can be obtained by the thermal decomposition of sodium or barium azide.
$Ba(N_3)_2(s) \xrightarrow{\Delta} Ba(s) + 3N_2(g)$
$2NaN_3(s) \xrightarrow{\Delta} 2Na(s) + 3N_2(g)$
Properties:
It is a colorless,odorless,tasteless,and non-toxic gas. It has very low solubility in water and low boiling and freezing points.
Uses:
$(i)$ Used in the manufacture of ammonia and other industrial chemicals containing nitrogen (e.g.,calcium cyanamide).
$(ii)$ Used to provide an inert atmosphere in iron and steel industries.
$(iii)$ Liquid dinitrogen is used as a refrigerant to preserve biological materials and food items,and in cryosurgery.
$(iv)$ It is used in the filling of electric bulbs to prevent oxidation of the filament.