Last Updated on March 9, 2023 by asifa
What is Dihydrogen?
Dihydrogen, Two hydrogen atoms react to form the homonuclear diatomic molecule known as dihydrogen. It is represented by H2 which is its molecular formula and the bond between the two hydrogen atoms is a covalent bond that satisfies the required duet configurations of both the atoms. Hydrogen being the lightest of the element that is in the modern periodic table makes dihydrogen to be the lightest known molecule existed. The hydrogen atom has a standard atomic weight of 1.008 u whereas the dihydrogen molecule has a molecular weight of 2.016 (a.m.u) atomic mass units.
The dihydrogen at standard conditions of temperature and pressure (i.e., at STP) exists as a gas that is colorless, does not have taste, and is odorless. This gas is believed to be highly combustible and flammable in nature. This gas can be used for various purposes and the Renewable hydrogen is considered to be a safe fuel as the by-product is only water during its combustion.
Structure of Dihydrogen
This molecule of Hydrogen consists of two hydrogen atoms covalently bonded. It consists of a linear shape and this molecule is nonpolar in nature. Both the hydrogen atoms that form the dihydrogen molecule are contributing one electron each for the formation of the covalent bond. Hence, all the requirements that are needed for this duet configuration of both the hydrogen atoms are satisfied. A figure showing the composition of dihydrogen is shown below:
Properties of Dihydrogen
- At the standard conditions of temperature and pressure, the dihydrogen molecule is in the gaseous state.
- Dihydrogen molecule has a melting point of 13.99 K. On the Celsius scale, its melting point is as low as -259.16 ℃. The boiling point on the other hand is around 20.27 K and on the Celsius scale, it is 252.879 ℃.
- The latent heat of fusion that is associated with the dihydrogen molecule is given to be 0.117 kJ per mole and the enthalpy of vaporization (also known as latent heat of vaporization associated with dihydrogen corresponds to around 0.904 kJ per mole.
- Dihydrogen molecule has a heat capacity corresponding to roughly around 28.83 J per mole Kelvin.
- When sound propagates via the gaseous dihydrogen, its speed of sound is around 1310 m/s.
Uses of Dihydrogen gas
The dihydrogen molecule has a lot of applications especially in chemical industries as well as the petroleum industry. There has been a demand for a large quantity of H2 in recent years for various purposes regularly.
- Dihydrogen is widely used and is required in the refining process of various fossil fuels and also in the manufacturing of ammonia.
- The petrochemical industry has become one of the main users of dihydrogen gas. It is being utilized in such industries for various chemical processes like hydrodealkylation, hydrodesulfurization, and also for hydrocracking.
- Dihydrogen gas has an application as a fuel where it is needed for running electric vehicles and also in fuel cells. Dihydrogen gas is believed to be the next source of energy or energy carrier which is free and non-polluting.
- For chemical preparation, this molecule can be used for the preparation of methanol which is required for various purposes.
- Similarly, it can also become a source of hydrogen for the production of high-demand hydrochloric acid (HCl).
- H2 or dihydrogen can be used as a reducing agent and is therefore helpful in the treatment of metallic ores.
Biochemistry of Dihydrogen
A dihydrogen molecule (H2) can be formed due to a certain form of anaerobic metabolism. This molecule can also be formed through various chemicals reactions by many microorganisms via a catalytic process using enzymes. The enzymes which are responsible for such catalyzed-biochemical reactions which lead to the release of dihydrogen are commonly called the hydrogenases, and these consist of Nickle or iron. These enzymes are capable of catalyzing a reversible redox reaction which contains two protons and two electrons on the reactant side and a dihydrogen molecule on the product side. During a pyruvate fermentation process, the dihydrogen gas is created after transferring the reducing equivalents to water. The term Hydrogen cycle refers to the natural cycle which involves the consumption and the production of hydrogen via various phases of the ecosystem.
Hazards that are associated with Dihydrogen
- Dihydrogen or H2 can react with most of the elements behaving as oxidizing agents or have enough oxidizing power. It has the capability of reacting with halogens namely chlorine, fluorine not in a safe path but rather spontaneous and violently, even when the reactions are taking place at very low temperatures close about to room temperature.
- The products that are formed after the reactions are mostly hydrogen halides such as hydrogen chloride and hydrogen fluoride respectively which are both considered potentially harmful acids.
- Hydrogen is very difficult to store and hence difficult to be carried around.
Read more: NCERT Solutions for Class 12 – Electrochemistry and Chemical kinetics