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Two atoms are contained in a molecule of dihydrogen, in which for both the atoms the nuclei are spinning. The types of hydrogen i.e. ortho and para hydrogen depend upon the nuclei’s direction of spin. If the spin of both the nuclei is in the same direction then it is known as ortho hydrogen molecules. If the spin of both the nuclei is in opposite direction then it is known as para-hydrogen molecules.
Ortho hydrogen
The dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in a similar direction are known as ortho hydrogen molecules. Simply it can be explained as the spin of two atoms aligned parallel to one another. The isomer of ortho hydrogen molecules occurs in a high hydrogen state as compared to para-hydrogen molecules. Ortho hydrogen forms a triplet state in NMR spectroscopy. Ortho hydrogen is a spin isomer of para-hydrogen.
Para Hydrogen
The dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in two opposite directions are known as para-hydrogen molecules. It simply means that in the H2 molecule each spin of an atom is opposite to each ortho, which means the spin of two atoms is aligned non-parallel to each other. Para hydrogen is the spin isomer of ortho hydrogen. The isomer of para hydrogen molecule occurs in a lower energy state as compared to ortho hydrogen molecule. Para hydrogen forms a singlet state in NMR spectroscopy.
Difference between ortho and para hydrogen
The key point in which ortho and para hydrogen differ in is that the dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in a similar direction are known as ortho hydrogen molecules whereas the dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in two opposite direction are known as para-hydrogen molecules.
The dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in a similar direction are known as ortho hydrogen molecules. | |
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Structure | |
In ortho hydrogen molecules there is a higher energy state. | |
Direction of Spin | |
Ortho hydrogen forms a triplet state in NMR spectroscopy. | |
The equilibrium mixture of ortho and para hydrogen is ordinary hydrogen.
Ortho Hydrogen Para Hydrogen
Both ortho and para hydrogen have similar chemical properties but there are differences in some physical properties, the difference in physical properties are as follows –
13.83K is the melting point of para-hydrogen and 13.95K is the melting point of ortho hydrogen.
20.36K is the boiling point of para-hydrogen and 20.39K is the boiling point of ortho hydrogen.
Para hydrogen has a lower internal molecular energy than ortho hydrogen possesses.
Along with the change in temperature, there is variation in ortho and para hydrogen –
As para-hydrogen is more stable, therefore at 0°K, hydrogen contains para hydrogen.
The ratio of para and ortho hydrogen, at the temperature of liquefaction of air is 1:1.
The ratio of ortho and para hydrogen at room temperature is 3:1.
The ratio of ortho to para-hydrogen at a very high temperature cannot be more than 3:1.
Conclusion
It is to conclude that the dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in a similar direction are known as ortho hydrogen molecules. Simply it can be explained as the spin of two atoms aligned parallel to one another. Whereas, the dihydrogen molecules which contain hydrogen atoms with the spinning of the nucleus in two opposite directions are known as para-hydrogen molecules. It simply means that in the H2 molecule each spin of an atom is opposite to each ortho, which means the spin of two atoms is aligned non-parallel to each other.
