Amongst all the elements around us in nature, hydrogen has the simplest atomic structure. It consists of one electron and one proton. However, it exists as a diatomic molecule (H2) in its elemental form and is referred to as dihydrogen. It also is the first element of the periodic table. Dihydrogen is the most abundant element in the universe. It makes us about 70% of the total mass of the universe. 

Hydrogen

Hydrogen is non-poisonous, odourless, tasteless, and colourless at ordinary temperatures. It is composed of three isotopes, and they are similar to each other in consideration of their chemical properties. These isotopes differ when the physical properties are considered because their atomic masses also differ. 

Physical properties of hydrogen

  • Hydrogen is colourless, tasteless, and odourless.
  • It is a combustible gas.
  • Hydrogen is lighter than air. 
  • It is not soluble in water.
  • The density of hydrogen is 0.09gL–1.

Chemical properties of hydrogen

The following reaction can illustrate the chemical properties of hydrogen – 

  • Reaction with metal ions and metal oxides – some metal ions are reduced in an aqueous solution while the metal oxides are reduced into corresponding metals.

Example: H2 (g) + 2M(g) 🡪 2MH(s)

  • Reaction with halogens – hydrogen halides are formed when reacted with halogens.

Example: H2 (g) + X2 (g) 🡪 2HX(g)

  • Reaction with dioxygen – water is formed after this highly exothermic reaction.

Chemical reaction: 2H2 (g) + O2 (g) 🡪 2H2O

  • Reactions with the organic compound – In the presence of catalysts, hydrogen produces many hydrogenated products. These products are useful for commercial purposes.

Example – Vegetable oils, when hydrogenated in the presence of nickel as a catalyst, produce edible fats.

Chemical reaction: H2+CO+RCH=CH2🡪RCH2CH2CHO

  • Reaction with dinitrogen – ammonia is formed when hydrogen is reacted with dinitrogen. This method is called the Haber process, and it is used to manufacture ammonia.

Chemical reaction: 3H2 (g) +N2 (g) 🡪 2NH3

Preparation of Hydrogen Gas

There are various methods of preparing hydrogen gas.

Laboratory preparation of hydrogen gas

Hydrogen is usually produced by the reaction of zinc with dilute hydrochloric acid. It is best to use granulated zinc for the process of preparing hydrogen. This is so because the acid reacts with it quickly to form hydrogen since granulated zinc provides more surface area. It also contains a small amount of copper, which acts as a catalyst in the process. Thus granulated zinc is preferred over pure zinc to produce hydrogen in the laboratory.

Procedure for preparing hydrogen with the reaction of zinc and dilute hydrochloric acid 

  • Place the granulated zinc in a flask.
  • Add the dilute hydrochloric acid into the flask containing granulated zinc through a thistle funnel.
  • The acid and zinc react with each other, producing hydrogen. 
  • The hydrogen gas produced passes through a delivery tube and is collected by the downward displacement of water. 

Chemical reaction

Zn + 2H+ → Zn2+ + H2

Procedure for preparing hydrogen with the reaction of zinc with aqueous alkali

Zinc is reacted with boiling aqueous alkali and forms hydrogen

Chemical reaction

Zn + 2NaOH → Na2ZnO2 + H2

Precautions to be taken in the laboratory while preparing hydrogen

Hydrogen is a combustible gas. So, it must be ensured that air inside all the apparatus being used has been removed. If neglected, an explosion can occur.

Commercial production of hydrogen

The different ways through which hydrogen is produced commercially is given below – 

  • In manufacturing sodium hydroxide and chlorine, hydrogen is obtained as a byproduct. The process involves the electrolysis of brine solution. During electrolysis, the reactions that take place are:

Over anode: 2Cl–(aq) → Cl2(g) + 2e–

Over cathode: 2H2O (l) + 2e–→ H2(g) + 2OH–(aq)

The overall reaction: 2Na+ (aq) + 2Cl–(aq) + 2H2O(l)↓Cl2(g) + H2(g) + 2Na+ (aq) + 2OH–(aq)

  • Platinum electrodes are used for the electrolysis of acidified water to produce Hydrogen.

Reaction: 2H2O (l) 🡪 2H2 (g) + O2 (g)

  • At high temperatures, the reaction of steam on hydrocarbons or coke in the presence of a catalyst produces hydrogen.

Reaction: CH4 (g) + H2O 🡪 CO (g) + 3H2

The mixture of CO and H2 is called water gas. As this mixture of CO and H2 is used for the synthesis of methanol and a number of hydrocarbons, it is also called synthesis gas or ‘syngas’.

  • Electrolyzing warm aqueous barium hydroxide solution between nickel electrodes produces high purity (>99.95%) dihydrogen.

The purpose for the preparation of hydrogen gas

There are several uses of hydrogen gas for which hydrogen gas is produced. The uses are as follows – 

  • It is used to produce Vanaspati fat.
  • Hydrogen chloride is manufactured with the help of hydrogen gas.
  • Methanol and several other organic chemicals are produced by using hydrogen.
  • Ammonia is manufactured using hydrogen, which further helps in manufacturing nitric acid.
  • It is used as rocket fuel.
  • Hydrogen helps in generating electric energy through fuel cells.
  • Hydrogen torches are used for welding purposes.

Conclusion

There are several methods of preparing hydrogen gas in the laboratory and commercially. However, we do not notice it in our daily lives. There are many applications of hydrogen gas in the manufacturing of certain chemicals that are used vastly. Moreover, hydrogen is used as a fossil fuel. The knowledge of the space that we have today of our solar system and the heavenly bodies beyond would not have been possible without the use of hydrogen.