What is the percentage of ortho and para hydrogen in ordinary hydrogen? How to calucate this?

Dear student,

Molecule of hydrogen spins about an axis. Hydrogen molecule in which both the proton in the nuclei of both H atoms are known as ortho hydrogen and if proton spins in opposite direction then it is termed as para hydrogen.

• At room temperature we get 75% ortho and 25% para form.
• At low temperature equilibrium shifts towards para form.
• At 25 K there is 99% para and 1% ortho hydrogen are seen.

With the help of quantum mechanics we can calculate the ortho and para hydrogen.
It predicts that a diatomic molecule has a set of rotational energy levels = $\frac{h^{2}J\left(J+1\right)}{8{\pi }^{2}I}$
where h = planck's constant
I = moment of inertia
J = rotational quantum number where J = 0,1,2....$\infty$
for para hydrogen J = 0,2,4
For ortho hydrogen J =1,3,5
So we can calculate ortho and para by this formula. It was derived by Raman spectra.


Regards