why is ortho hydrogen more stable than para hydrogen???

Dear student,

A molecule of diatomic hydrogen (hydrogen gas) contains two hydrogen atoms. The nucleus of each aton (a protron) is spinning. Depending upon the direction of the spin of the two nuclei, the hydrogens are of two types: ortho or para.

Ortho-hydrogen molecules are those in which the spins of both the nuclei are in the same direction. Para-hydrogen is when the spins of both the nuclei are in the opposite directions.

Ordinary hydrogen gas is an equilibrium mixture of ortho and para hydrogen. The amount of ortho- and para-hydrogen varies with temperature.

At 0°K, hydrogen contains mainly para-hydrogen which is more stable. At the temperature of liquid of air, the ratio of ortho- and para-hydrogen is 1 : 1.

At the room temperature, the ratio of ortho- to para-hydrogen is at its maximum of 3 : 1. Even at very high temperatures, the ratio of ortho- to para-hydrogen can never be more than 3 : 1. So, it is possible to get pure para hydrogen by cooling ordinary hydrogen gas to a very low temperature (close to 20 K) but it is never possible to get a sample of hydrogen containing more than 75% of ortho hydrogen.

What happens is that in para the spins of the proton is opposite leading to a bit of disagreement between the atoms of combined hydrogen. While in ortho the protons have same spin and are in complete harmony with each other.as a result hydrogen prefers to go for harmont rather than disagreement. But not everything can be perfect , can it?

O.K., this can be a bit confusing because there are two different ways to use the words ortho and para in chemistry. One refers to the position of the hydrogens on a substituted benzene molecule. Ortho hydrogens are the ones next to the substituent, para is the one on the opposite side of the molecule. That is not, I suspect what you wanted to know.Hydrogen atoms consist of a proton and an electron. The proton has a charge of +1 and a spin. The spin can either be clockwise or counter-clockwise. So when you have a hydrogen molecule you have two possibilities: the two spins can both be aligned (both clockwise or both counter-clockwise) or they can be opposed: Ortho hydrogen has the spins aligned, para hydrogen has the spins opposite. In the above picture think of your hand wrapping around the hydrogen atom with your fingers pointing in the direction of the spin. If the spin is counter-clockwise and you are using your right hand, your thumb will point up. If it is clockwise, your thumb will point down. The arrows in the picture are the direction your right thumb would point.The amount of ortho and para hydrogen varies with temperature as:At 0°K, hydrogen contains mainly para hydrogen which is more stable.At the temperature of liquefaction of air, the ratio of ortho and para hydrogen is 1 : 1.At the room temperature, the ratio of ortho to para hydrogen is 3 : 1.Even at very high temperatures, the ratio of ortho to para hydrogen can never be more than 3 : 1.Thus, it has been possible to get pure para hydrogen by cooling ordinary hydrogen gas to a very low temperature (close to 20 K) but it is never possible to get a sample of hydrogen containing more than 75% of ortho hydrogen.