Nitrogen and equations of reactions with it

What properties are typical for nitrogen?

Nitrogen in discharge tube [Wikimedia]

Ni­tro­gen is an el­e­ment of the 15ᵗʰ group of the sec­ond pe­ri­od in the Pe­ri­od­ic Ta­ble (by the new clas­si­fi­ca­tion). In na­ture it is en­coun­tered in the form of two iso­topes (atoms with an iden­ti­cal atom­ic num­ber, but dif­fer­ent mass num­bers) – with the mass num­bers of 14 and 15. Ni­tro­gen makes up around 78% of the vol­ume of the air. This gas is one of the most abun­dant on Earth.

Phys­i­cal prop­er­ties

By its phys­i­cal prop­er­ties, ni­tro­gen is a col­or­less gas with­out smell or taste. The boil­ing point of ni­tro­gen is -195.75 ᵒC (-320.35 ᵒF). The gas is chem­i­cal­ly in­ert.

Liquid nitrogen [Wikimedia]

Ob­tain­ing ni­tro­gen

One of the lab­o­ra­to­ry meth­ods for ob­tain­ing molec­u­lar ni­tro­gen is the de­com­po­si­tion of am­mo­ni­um ni­trate NH₄NO₂:

NH₄NO₂ = N₂ + 2H₂O (first heat­ing is re­quired, then the ves­sel is cooled down dur­ing the re­ac­tion, as the process takes place with the re­lease of a great amount of heat – up to kJ). The ni­tro­gen is con­tam­i­nat­ed with im­pu­ri­ties – ni­tro­gen ox­ides and am­mo­nia. Ni­tro­gen can also be ob­tained in the ther­mal de­com­po­si­tion of am­mo­nia and ni­tro­gen (I) ox­ide:

  1. 2NH₃ = N₂ + 3H₂;

  2. 2N₂O = 2N₂ + O₂.

Pur­er molec­u­lar ni­tro­gen can be ob­tained in the de­com­po­si­tion of azides, and in pass­ing am­mo­nia over cop­per (II) ox­ide:

  • 2NaN₃ = 2Na + 3N₂;
Sodium azide NaN₃ [Wikimedia]
  • 3CuO + 2NH₃ = N₂ + 3Cu + 3H₂O the process takes place at 700 ᵒC (1292 ᵒF); cop­per ox­ide is tak­en in an amount that ex­ceeds the cal­cu­lat­ed amount by two times, and am­mo­nia is ob­tained for the re­ac­tion by heat­ing its con­cen­trat­ed so­lu­tion).

In in­dus­try, ni­tro­gen is ob­tained by dis­till­ing liq­ue­fied air.

Ox­i­da­tion states of ni­tro­gen

The atom can re­ceive elec­trons to com­plete the out­er lay­er, and give them away – this ex­plains the large num­ber of pos­si­ble ox­i­da­tion states for the ni­tro­gen atom.

Ni­tro­gen dis­plays all ox­i­da­tion states from -3 to +5: -3, -2, -1, 0, +1, +2, +3, +4, +5. Com­pounds in which ni­tro­gen has the low­est ox­i­da­tion state dis­play typ­i­cal­ly re­duc­ing prop­er­ties, while com­pounds with ni­tro­gen in the high­est ox­i­da­tion state are strong ox­i­diz­ers. Oth­er com­pounds, de­pend­ing on the sec­ond reagent or con­di­tions of the re­ac­tion may dis­play ox­i­da­tion-re­duc­tion du­al­i­ty – dis­play both ox­i­da­tion and re­duc­tion prop­er­ties (this is es­pe­cial­ly char­ac­ter­is­tic for ni­tro­gen (III) ox­ide).

Ex­am­ples of com­pounds in which ni­tro­gen dis­plays dif­fer­ent ox­i­da­tion states:

  • NH₃, NH₄­Cl, Ca₃N₂ – ox­i­da­tion state -3 (am­mo­nia, am­mo­ni­um salts, ni­trides);

  • N₂H₄ – ox­i­da­tion state -2 (hy­drazine);

  • NH₂OH – ox­i­da­tion state -1 (hy­drox­y­lamine);

  • N₂ – ox­i­da­tion state 0 (molec­u­lar ni­tro­gen);

  • N₂O – ox­i­da­tion state +1 (ni­tro­gen (I) ox­ide);

  • NO – ox­i­da­tion state +2 (ni­tro­gen (II) ox­ide);

  • N₂O₃, HNO₂, NaNO₂ – ox­i­da­tion state +3 (ni­tro­gen (III) ox­ide, ni­trous acid, ni­trites);

Sodium nitrite crystals [Wikimedia]
  • NO₂ – ox­i­da­tion state +4 (ni­tro­gen (IV) ox­ide)

  • N₂O₅, HNO₃, KNO₃ – ox­i­da­tion state +5 (ni­tro­gen (V) ox­ide, ni­tric acid, ni­trates).

Ni­tro­gen dis­plays typ­i­cal non-metal­lic prop­er­ties and has high elec­tri­cal con­duc­tiv­i­ty (it is third af­ter flu­o­rine and oxy­gen by this pa­ram­e­ter).

Chem­i­cal prop­er­ties of molec­u­lar ni­tro­gen

Ni­tro­gen is a gas that does not sup­port breath­ing, rot­ting and ox­i­da­tion. Ow­ing to its in­ert­ness, this gas is of­ten used to cre­ate non-re­ac­tive at­mos­pheres. The most im­por­tant and prac­ti­cal re­ac­tions with molec­u­lar ni­tro­gen (be­cause of its chem­i­cal in­ert­ness the gas does not re­act with many sub­stances):

  • re­ac­tion with hy­dro­gen with heat­ing (from 500 ᵒC or 932 ᵒF and high­er de­pend­ing on the re­quire­ments for the speed of re­ac­tion and out­put), high pres­sure (around 350 at­mos­pheres) and in the pres­ence of a cat­a­lyst (for ex­am­ple, Fe or FeO):

N₂ + 3H₂ = 2NH₃;

  • re­ac­tion with oxy­gen with for­ma­tion of ni­tro­gen (II) ox­ide:

N₂ + O₂ = 2NO (se­lec­tive re­ac­tion, takes place with heat­ing);

  • re­ac­tion with met­als with heat­ing (apart from lithi­um, which re­acts with it at room tem­per­a­ture):

3Ca + N₂ = Ca₃N₂ (cal­ci­um ni­tride forms);

6Li + N₂ = 2Li₃N (lithi­um ni­tride forms);

  • re­ac­tion with boron at high tem­per­a­ture:

2B + N₂ = 2BN;

Boron [Wikimedia]
  • re­ac­tion with cal­ci­um car­bide at 1000 ᵒC (1832 ᵒF):

CaC₂ + N₂ = CaC­N₂ + C;

  • re­ac­tion with acety­lene:

С₂Н₂ + N₂ = 2HCN (takes place in a con­densed dis­charge);

  • re­ac­tion with sodi­um car­bon­ate and coal with heat­ing:

2Na₂­CO₃ + 8C + 2N₂ = 4NaCN + 6CO;

  • re­ac­tion with hot coal:

2C + N₂ = (CN)₂ (di­cyanogen forms);

  • re­ac­tion with flu­o­rine with heat­ing (or with an elec­tri­cal dis­charge):

N₂ + 3F₂ = 2NF₃ (ni­tro­gen flu­o­ride forms).

Ex­per­i­ments with ni­tro­gen are in­clud­ed in MEL Chem­istry sub­scrip­tion.

With oth­er halo­gens and sul­fur ni­tro­gen does not re­act (sul­fides and halo­genides are ob­tained in­di­rect­ly). Ni­tro­gen does not re­act with acids, al­ka­lis or wa­ter.

Ammonium carbonate [Wikimedia]

Ni­tro­gen has found wide ap­pli­ca­tion in in­dus­try. It is used as a pow­er­ful cool­ing agent and sub­stance re­quired for cre­at­ing in­ert at­mos­pheres. Ni­tro­gen is of­ten used as an al­loy­ing ad­di­tive for sil­i­con, and also in air­craft con­struc­tion and in fire-fight­ing. Am­mo­ni­um salts (and am­mo­ni­um hy­drox­ide) are used in medicine, and salt­peter is used in agri­cul­ture as fer­til­iz­er.