(i) In the laboratory, dinitrogen is prepared by treating an aqueous solution of ammonium chloride with sodium nitrite.

${\text{NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)+{\text{NaNO}}_{\text{2}}\left(\text{aq}\right)\to {\text{N}}_{\text{2}}\left(\text{g}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)+\text{NaCl}\left(\text{aq}\right)$

Small amounts of $\text{NO}$ and ${\text{HNO}}_3$ are also formed as impurities, which can be removed by passing the gas through aqueous sulphuric acid containing potassium dichromate.

(ii) Dinitrogen can also be prepared by heating ammonium dichromate

$\left({\text{NH}}_4\right){}_2{\text{Cr}}_2{\text{O}}_7\left(\text{s}\right)\stackrel{\text{Δ}}{⟶}{\text{N}}_2\text{(g)}+{\text{4H}}_2\text{O}\left(\text{l}\right)+{\text{Cr}}_2{\text{O}}_3\left(\mathrm{s}\right)$

(iii) Copper metal reacts with dilute ${\text{HNO}}_3$ to form nitrogen (II) oxide $\left(\text{NO}\right)$

$3\mathrm{C}\mathrm{u}\left(\mathrm{s}\right)+8\mathrm{H}\mathrm{N}{\mathrm{O}}_3\mathrm{ }\left(\mathrm{d}\mathrm{i}\mathrm{l}\mathrm{u}\mathrm{t}\mathrm{e}\right)\to \mathrm{ }3\mathrm{C}\mathrm{u}{\left(\mathrm{N}{\mathrm{O}}_3\right)}_2\left(\mathrm{a}\mathrm{q}\right)\mathrm{ }+2\mathrm{N}\mathrm{O}\left(\mathrm{g}\right)+4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

(iv) Copper metal reacts with conc. ${\text{HNO}}_3$ to form nitrogen (IV) oxide or nitrogen dioxide $\left({\text{NO}}_{\text{2}}\right).$

$\text{Cu}\left(\text{s}\right){\text{+4HNO}}_{\text{3}}\left(\text{conc}\text{.}\right)\to \text{Cu}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right){\text{+2NO}}_{\text{2}}\left(\text{g}\right){\text{+2H}}_{\text{2}}\text{O}\left(\text{l}\right)$