Chemical reactions with the release of hydrogen
Methods for obtaining hydrogen
Hydrogen is an abundant element in nature and in the universe, which holds first place in the Periodic Table.
For example, hydrogen is present in water, practically all organic substances, stars and interstellar gas, galactic planets etc., so it is difficult to overestimate the importance of this element in the world and the universe. It is rarely encountered in free form; the volume content of hydrogen in the air is around 5∙10-5. Hydrogen H₂ is a light gas which has no smell, color or taste.
Obtaining pure hydrogen in the laboratory is considered to be one of the most dangerous experiments, because H₂ is an explosive and combustible gas in combination with air.
Hydrogen itself is harmless for human life and is non-toxic. It should also be noted that this gas dissolves in ethanol and several metals such as iron, nickel, titanium etc.
The history of obtaining hydrogen
As for the history of obtaining hydrogen, this gas has been extracted ever since chemistry became a separate science, and the release of a combustible gas was observed in the interaction of metals and acids.
Previously in alchemy, the combustible gas released was known as phlogiston, a hypothetical superfine substance made of fire, which filled all combustible substances and was released from them at the moment of combustion. But the renowned Russian polymath Mikhail Lomonosov showed that in these reactions phlogiston was not released. In 1766, this gas was called inflammable air by the scientist Henry Cavendish. At the moment of combustion, this gas actively released water, but Cavendish’s belief in alchemic lore concerning the fiery substance hindered him from drawing objective conclusions. Later in 1766, it was established that inflammable air was present in water, and could be extracted from it. These conclusions were made by Antoine Lavoisier and Jean Meusnier.
Areas of application
Hydrogen is actively used in the chemical industry for the manufacture of many substances, for example ammonium, methanol, and H₂ is also used for making soap and plastics.
In the food industry, margarine is made with hydrogen. Hydrogen is also used in aircraft construction for inflating airships, but because of its explosiveness it was replaced with helium.
At present studies are being conducted on replacing the traditional fuel of petrol with hydrogen fuel.
Reactions with the release of hydrogen
At present, the most widespread method of obtaining hydrogen on an industrial scale is the conversion of methane CH₄ or natural gas. Methane is a natural gas, a simple hydrocarbon. When methane is heated with water vapors at high temperatures (1000 °С), hydrogen is released:
CH₄ + Н₂О→ C + 2H₂
In industry, hydrogen is also obtained by passing water over red-hot coke.
Obtaining hydrogen with Kipp’s apparatus.
Kipp’s apparatus is the best-known device for obtaining gases, and consists of a flask, funnel and gas pipe. With this apparatus, hydrogen is obtained with zinc and hydrochloric and sulfuric acid. The apparatus makes it possible to collect gas in a test tube or other container, but experiments with the release of H₂ can also be carried out without it, simply by adding a piece of zinc and hydrochloric acid to a test tube:
Zn + 2HCl → ZnCl₂ + H₂↑.
The reaction with the release of hydrogen from aluminum and alkali makes it possible to obtain purer hydrogen. This experiment can be carried out in the open air, by filling an ordinary balloon with hydrogen. It must not be carried out at home, as the experiment is potentially highly explosive.
2Al + 2NaOH + 6H₂O → 2Na[Al(OH)₄] + 3H₂↑
Here you’ll find safe experiments to do at home.
Instead of aluminum, you can use aluminum foil: add it to a solution of sodium hydroxide.
Sodium hydroxide is an ordinary fluid used for cleaning pipes which can be purchased at a hardware store. If you fill a balloon with hydrogen, by placing it over a flask from which the gas is released, the balloon will rise into the air. Obtaining hydrogen by this method is quite easy to explain: the surface of the aluminum is covered by a special oxide film, which starts to break down on interaction with alkalis.
Reaction with the release of hydrogen using copper sulfate, aluminum and salt
Add kitchen salt (sodium chloride) and copper sulfate CuSO₄∙5Н₂О to a flask. Then add water. The resulting mixture should turn green, but if the liquid remains transparent, add more salt and copper sulfate. Then add pieces of aluminum or foil rolled into a ball to the flask. The reaction of the release of hydrogen will begin, as the copper chloride that forms in the flask will remove the oxide film from the aluminum.
Reaction with the release of hydrogen using alkaline and alkaline earth metals and water.
Lithium is a light alkaline metal which does not sink in water. If you add a piece of lithium to lukewarm water, an immediate reaction with the release of gas will take place:
Li + H2O = LiOH + H₂↑.
Thus, when alkaline metals come into contact with water, alkali forms and hydrogen is released.
Reaction of the release of hydrogen using calcium and water
Calcium is a soft alkaline earth metal, and if you add purified metallic calcium to water, a violent reaction takes place with the release of hydrogen and calcium hydroxide:
Ca + 2H₂O → Ca(OH)₂↓ + H₂↑
Thus, when alkaline earth metals come into contact with water, a base forms and hydrogen is released.
Obtaining hydrogen by electrolysis
The simplest method to obtain hydrogen by electrolysis is the hydrolysis of water. This method can be used to obtain pure oxygen and hydrogen in the laboratory.
2Н₂О = 2Н₂↑ + О₂↑