p Block Elements
9.0 Group $15$-The Nitrogen Family
9.0 Group $15$-The Nitrogen Family
Occurrence:
Nitrogen is widely distributed in nature both in free as well as in the combined state. Air is the most abundant source of free nitrogen. It forms 75% by mass and 78% by volume of the air. In the combined state, It is found as nitrates such as Chile Saltpetre $NaN{O_3}$, Indian Saltpetre $KN{O_3}$ and ammonium compounds.
Preparation:
Nitrogen can be obtained from the following two sources:
(i) Nitrogen compounds
(ii) Air
$(I)$ Nitrogen from nitrogen compounds:
(a) Nitrogen in the laboratory can be obtained by heating ammonium nitrate or ammonium dichromate.
$$\begin{equation} \begin{aligned} N{H_4}Cl + NaN{O_2} \to N{H_4}N{O_2} + NaCl \\ N{H_4}N{O_2} \to {N_2} + 2{H_2}O \\ (N{H_4})C{r_2}{O_7} \to {N_2} + C{r_2}{O_3} + 4{H_2}O \\\end{aligned} \end{equation} $$
Nitrogen is collected by downward displacement of water.
(b) Pure nitrogen can be obtained by passing the ammonia vapours over heated $CuO$.$$2N{H_3} + 3CuO \to {N_2} + 3Cu + 3{H_2}O$$
$N{H_3}$ can also be oxidised to nitrogen by $Cl_2,Br_3$, a hypochlorite, a hypobromite or bleaching powder.
(c) It can be obtained in small amounts by heating sodium or barium azides in vaccum.$$N{H_2}CON{H_2} + 2HN{O_2} \to 2{N_2} + C{O_2} + 3{H_2}O$$
(d) Pure nitrogen is obtained in small amounts by heating sodium or barium azides in vacuum.$$Ba{({N_3})_2} \to 3{N_2} + Ba$$
$(II)$ From air:
(a) Commercially nitrogen is obtained by liquefication of air.The resultant liquid is fractionally distilled in Claude's apparatus.
(b) By removing oxygen from the air with the use of chemical substances.
$CO_2$ and $Co$ are removed by usual methods.
Properties:
(i) It is a colorless, tasteless and odorless gas. it is slightly lighter than air as its vapor density is $14.0$. It is sparingly soluble in water.
(ii) It can be liquefied to a colorless liquid $b.pt - 195.8^\circ C$
(iii) It does not help in combustion. Nitrogen itself is non-combustible.
(iv) It is chemically inert under ordinary conditions. However, it shows chemical activity under high temperatures
.
(V) Nitrogen combines with oxygen under the influence of very high temperature like electric spark.
\[{N_2} + {O_2}\overset {3000^\circ C} \leftrightarrows 2NO\;(Nitric\;Oxide)\]
(vi) Nitrogen combines with hydrogen in the presence of a catalyst (finely $s$ = divided iron) at $200$ atmosphere and $400 - 500^\circ C$ temperature.
\[{N_2} + 3{H_2} \rightleftarrows 2N{H_3}\;(Ammonia)\]
(vii) Nitrogen combines with metals at red heat to form nitrides.\[\begin{gathered} 6Li + {N_2}\xrightarrow{{450^\circ C}}2L{i_3}N\;(Lithium\;Nitride) \hspace{1em} \\ 3Mg + {N_2}\xrightarrow{{450^\circ C}}M{g_3}{N_2}\;(Magnesium\;Nitride) \hspace{1em} \\ 2Al + {N_2}\xrightarrow{{800^\circ C}}2AlN\;(Alu\min ium\;Nitride) \hspace{1em} \\ \end{gathered} \]
Non-Metals like boron.silicon at bright red heat also combine with nitrogen.\[\begin{gathered} 2B + {N_2} \to 2BN{\kern 1pt} (Boron\;Nitride) \hspace{1em} \\ 3Si + 2{N_2} \to S{i_3}{N_4}{\kern 1pt} (Silicon\;Nitride) \hspace{1em} \\ \end{gathered} \]
(viii) Nitrogen combines with calcium carbide to form calcium cyanamide at $1000^\circ C$$$Ca{C_2} + {N_2} \to CaC{N_2} + C$$
The mixture of calcium cyanamide and carbon is technically known as nitrolinm.
Uses: It is used in the manufacture of $N{H_3},HN{O_3},CaC{N_2}$ and other nitrogen compounds.
