Nitrogen and oxygen and their interaction
We consider nitrogen inert. But is it?
This article will discuss oxygen and nitrogen – two gases that readily react with each other.
It's hard to pinpoint the first scientist to obtain nitrogen, but Henry Cavendish was certainly among them. In his laboratory in 1772, Cavendish used a special device to pass air over heated coals. After repeating this process several times, he then treated the air with alkalis. Cavendish called the substance obtained in the experiment a “suffocating” gas because of its properties. But the scientist couldn’t understand just what the suffocating gas was. Armed with modern chemistry knowledge, however, we can reason that passing air over heated coals binds carbon dioxide, and that the alkali neutralizes it. The remaining "suffocating" part of the air consists, for the most part, of molecules of N₂.Cavendish reported his findings to his colleague, Joseph Priestley.
Intriguingly, this is not the first case when scientists did not understand the substance that they had created in their experiments. For example, Priestley once bonded oxygen and nitrogen using electric current, but did not understand that he had obtained argon, an inert gas.
Physical properties of nitrogen
In standard conditions, nitrogen is an inert, colorless gas with no smell or taste. It is harmless to human beings, and is lighter than air, but isn’t as light as helium or hydrogen. The gas is also virtually insoluble in water and does not react with it.
The seventh element in the periodic table can also exist in liquid and solid aggregate states.
In a liquid state, nitrogen boils at -195.8 °C, whereas in a solid state it melts at -209.86 °C.
Nitrogen molecules are quite stable; they are diatomic and form a triple bond. Thus, the molecules practically never break apart, and the seventh element demonstrates low chemical activity. Conversely, nitrogen compounds are highly unstable – heating them forms free nitrogen.
Reactions with metals
Molecular nitrogen can only enter into a reaction with a small group of metals, all of which display reducing properties. For example, N₂ can react with lithium:
6Li + N₂ = 2Li₃N
It also reacts with the light-silvery metal magnesium, but only at temperatures above 300 °C. This reaction yields magnesium nitride – yellow-green crystals which, when heated, break down into magnesium and free nitrogen:
3Mg + N₂ = Mg₃N₂.
Mg₃N₂ → 3Мg + N₂↑— at a temperature of 1000 °C or higher.
If the nitride of an active metal is added to water, the process of hydrolysis begins, yielding the hydroxide of the metal and ammonium.
Nitrogen and hydrogen
Nitrogen and hydrogen react at a temperature of around 400 °C, with a pressure of 200 atmospheres and in the presence of porous iron acting as a catalyst:
3H₂ + N₂ = 2NH₃.
Reaction of nitrogen and other non-metals
All interactions of substances with nitrogen take place at high temperatures. Take, for example, boron:
2B + N₂ = 2BN
It does not interact with many halogens, or with sulfur, but sulfides and halogenides may be obtained indirectly.
Reaction of nitrogen with oxygen
Oxygen is an element with the atomic number 8. It is a transparent gas with no smell or color, and is blue in its liquid form.
Oxygen can also exist in a solid aggregate state of blue crystals. It has diatomic molecules.
Interestingly, Priestley did not initially understand that he had discovered oxygen, and believed that he had obtained a certain component of air. Priestley observed the breakdown of mercury oxide in a hermetic device. The scientist used a lens to direct rays of sunlight to the oxide.
As for the interaction of nitrogen and oxygen, the substances react in the presence of an electric current, because nitrogen is a stable molecule and reacts unwillingly with other substances:
O₂ + N₂ = 2NO
There are several oxides of nitrogen, the oxidation state of which varies from one to five.
Several compounds can form from a reaction between nitrogen and oxygen:
N₂O — nitrous oxide;
NO — nitric oxide;
N₂O₃ — dinitrogen trioxide;
NO₂ — nitrogen dioxide;
N₂O₅ — nitrogen pentoxide.
Nitrous oxide, an anesthetic, is obtained via the breakdown of ammonium nitrate. It is a colorless gas with a characteristic pleasant smell. The oxide dissolves well in water.
N₂O is also a constant component of air. The process takes place at a temperature of 200 °C. The reaction is:
NH₄NO₃ = 2Н₂О + N₂O↑
Nitric oxide, NO, is also a colorless gas that is almost insoluble in water. This compound does not readily release oxygen, but it is known for its addition reactions, such as with toxic, green-yellow chlorine gas:
2NO + Сl₂ = 2NOCl.