Question

ortho and para hydrogen difference

Answer 1

Ortho hydrogen molecules are those in which the spins of both the nuclei are in the same direction.
 Molecules of hydrogen in which the spins of both the nuclei are in the opposite direction are called para hydrogen.

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.  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.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.