Chemistry Formulas

Hydrogen Formula

The hydrogen is a colourless, odourless, tasteless, and at the same time a flammable gaseous substance that is one of the simplest members of the family of the chemical elements. The Hydrogen Formula has an atom that has a nucleus that contains a proton bearing 1 unit of positive electrical charge, moreover, an electron, bearing 1 unit of negative electrical charge, is associated with this nucleus as well. However, under some normal conditions, the hydrogen gas is a loose aggregation of the molecules of the hydrogen, each of them consists of a pair of atoms, a diatomic molecule i.e. H2.

Hydrogen Formula and Structure

The hydrogen has a chemical formula i.e. H2. In addition, its molar mass depends on the hydrogen isotope that you will be considering. The hydrogen that forms with 2 nuclei with 1 proton each one, has a molar mass of 200 g/mol, the deuterium forms by 2 nuclei with 1 proton and 1 neutron each one, has a mass of 400 g/mol. And the tritium that forms through 2 nuclei with 1 proton and 2 neutrons each one, has a mass of 600 g/ml. moreover, this molecule forms by 2 hydrogen atoms that are joined by 1 ionic bond. We can write its chemical structure as we are showing below, in the common representations used for the organic molecules.

H – H


The hydrogen is very abundant gas in the whole universe, however, on the planet Earth it is found in the traces of the atmosphere and in some planets and stars like Jupiter and the Sun, etc. We can also produce it with the help of some micro-organisms.


We can prepare it through various methods, such as:

We can produce it by the process of electrolysis of the water that results in the molecular oxygen and hydrogen:

2H2O → 2H2 + O2

When we produce it with the help of the micro-organisms, the H2 is biosynthesized due to the action of the enzymes that we refer to as the hydrogenases.

Physical Properties

Hydrogen is a gas that has no colour. This gas has a density of 0.089 g/ml. Its melting point is about 260 °C, whereas, its boiling point is about 252 °C.

Chemical Properties

This chemical compound is very reactive because the mixtures with the air can be explosive too, but only when the temperature is up to 500 °C or more. At the normal room temperature, it is not reactive anymore. Moreover, the hydrogen gas can react with various types of other elemental compounds as well, just like the halogens to form the hydrides and the acids also:

Cl2 + H2 → 2HCl

S2 + 2H2 → 2H2S


The hydrogen gas is useful as a reactant in the production process of the ammonia and some acids like the HCl and H2S. We also use it in the production of petroleum oil.

Solved Example for You:

Question: The metal X is prepared by the process of electrolysis of fused chloride. It reacts with the hydrogen to make a colorless solid from which hydrogen is released on treatment with the water. This metal is:

(A). Al.

(B). Ca.

(C). Cu.

(D). Zn.

Answer: (B). Ca.


The calcium is obtained by the process of electrolysis of the CaCl2. Ca reacts with the hydrogen to produce calcium hydride (CaH2) which is a solid that has no colour.

The calcium hydride reacts with the water to make calcium hydroxide and dihydrogen gas at the same time:

CaCl2 + H2 + 2 Na → CaH2 + 2 NaCl

Therefore, the correct option is (B) i.e. Ca.

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