Ni­tro­gen (II) ox­ide is a non-salt-form­ing ox­ide, a poi­sonous gas with­out col­or or smell which dis­solves poor­ly in wa­ter. Ni­tro­gen (II) ox­ide is ca­pa­ble of par­tial­ly dimer­iz­ing (a dimer is a com­pound con­sist­ing of two sim­pler iden­ti­cal mol­e­cules). Boil­ing point is -152 ᵒC or -242 ᵒF.

Ob­tain­ing ni­tro­gen (II) ox­ide

NO is the only ni­tro­gen ox­ide which can be ob­tained from sim­ple sub­stances:

N₂ + O₂ = 2NO (an elec­tric charge or heat­ing to 1200-1300 ᵒC or 2192-2372 ᵒF is re­quired).

In the lab­o­ra­to­ry and in in­dus­try, oth­er re­ac­tions are used. In the lab­o­ra­to­ry, di­lut­ed ni­tric acid is used:

3Cu + 8H­NO₃ = 2NO + 3Cu(NO₃)₂ + 4H₂O.

In in­dus­try, cat­a­lyst ox­i­da­tion of am­mo­ni­um is used with a plat­inum-rhodi­um cat­a­lyst with heat­ing:

4NH₃ + 5O₂ = 4NO + 6H₂O (nec­es­sary tem­per­a­ture around 700 ᵒC or 1292 ᵒF).

Chem­i­cal prop­er­ties

Ni­tro­gen (II) ox­ide does not re­act with wa­ter and prac­ti­cal­ly does not dis­solve in it. By its na­ture it is non-salt-form­ing – salts can­not be ob­tained from this ox­ide by re­ac­tions. In com­pounds, the ox­i­da­tion state of ni­tro­gen is +2, and no ni­tro­gen-con­tain­ing acids cor­re­spond to this ox­ide (acid can­not be ob­tained from this ox­ide by di­lut­ing). De­pend­ing on the type of re­ac­tion, ni­tro­gen (II) ox­ide may be an ox­i­diz­er or re­duc­er. The most im­por­tant chem­i­cal prop­er­ties of the sub­stance are the fol­low­ing.

On a rhodi­um cat­a­lyst, ni­tro­gen (II) ox­ide may ox­i­dize car­bon monox­ide to car­bon diox­ide:

2NO + 2CO = 2CO₂ + N₂:

It can ox­i­dize sul­fur diox­ide to tri­ox­ide:

2NO + 2SO₂ = 2SO₃ + N₂.

Al­ka­line caus­es a dis­pro­por­tion­a­tion re­ac­tion to be­gin – “self-ox­i­diz­ing-self-re­duc­ing” – some of the ni­tro­gen atoms ox­i­dizes, and oth­ers re­duce:

6NO + 4KOH = N₂ + 4KNO₂ + 2H₂O (in a flux).

The com­pound may en­ter into com­bi­na­tion re­ac­tions with halo­gens:

2NO + Cl₂ = 2N­O­Cl (this re­ac­tion takes place in at a cold tem­per­a­ture).

NO₂ is a brown gas - and it`s quite easy to turn NO to NO₂

Com­bi­na­tion be­tween ni­tro­gen (II) and (III) ox­ides may also be­gin:

NO + NO₂ = N₂O₃.

Ox­i­da­tion of ni­tro­gen (II) ox­ide

In ox­i­da­tion re­ac­tions, ni­tro­gen (II) ox­ide is a re­duc­er – for its ox­i­da­tion by oxy­gen to be­gin, no spe­cial con­di­tions are re­quired.

2NO + O₂ = 2NO₂ (the gas turns brown, as the ox­ide with ni­tro­gen at an ox­i­da­tion state of is a brown gas).

Here you can find ex­per­i­ments with ni­tro­gen diox­ide.

In an acidic medi­um, ox­i­da­tion of potas­si­um per­man­ganate is also pos­si­ble:

5NO + 3KM­nO₄ + 2H₂­SO₄ = 2Mn­SO₄ + 3KNO₃ + Mn(NO₃)₂ + 2H₂O.

Gas only dis­plays ox­i­da­tion prop­er­ties in re­ac­tions with bet­ter re­duc­ers that sur­pass its re­duc­tion abil­i­ty. The first ox­i­da­tion re­ac­tion of ni­tro­gen (II) ox­ide by oxy­gen is nec­es­sary for the man­u­fac­ture of ni­tric acid, as this type can­not be ob­tained di­rect­ly from its ox­ide. Ni­tric acid can be ob­tained by ni­tro­gen IV ox­ide by the fol­low­ing re­ac­tion (there must be a sur­plus of oxy­gen):

4NO₂ + О₂ + 2H₂O = 4H­NO₃.

Of­ten the ni­tro­gen ox­ide re­quired for this re­ac­tion is ob­tained from NO, as it is quite easy to ox­i­dize this gas to the re­quired NO₂ (spe­cial con­di­tions are not re­quired for this).

Of­ten ni­tro­gen (II) ox­ide NO is used for the man­u­fac­ture of ni­tric acid. The gas has great bi­o­log­i­cal and bio­chem­i­cal sig­nif­i­cance, as it takes part in the life ac­tiv­i­ty process. The sub­stance is also a reagent for con­duct­ing cer­tain chem­i­cal re­ac­tions – for ex­am­ple ob­tain­ing ni­tric acid.