Nitrogen and equations of reactions with it
What properties are typical for nitrogen?
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.
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.
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:
2NH₃ = N₂ + 3H₂;
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;
- 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);
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;
- 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.
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.