Which is more stable: Ortho or Para Hydrogen? It is known that Para-Hydrogen has opposite spin and Ortho-Hydrogen has same spin.
Therefore, the energy of Para-Hydrogen is lower than that of Ortho-Hydrogen.
Therefore, the stability order should be: Para-Hydrogen &gt; Ortho-Hydrogen.
Is this true or is the stability order the opposite of what I predicted?. What is the reason for this stability order?
At room temperature, about $75$% of $\ce{H2}$ is $\ce{o-H2}$ and $25$% is $\ce{p-H2}$. As the temperature drops, the relative amounts of $\ce{p-H2}$ increases. The two forms are in a temperature-dependent equilibrium $\ce{o-H2&lt;=&gt; p-H2}$, $\Delta H = \pu{-1.66 kJ/mol}$.
Ref. M. Eagleson, Concise Encyclopedia Chemistry, Walter de Gruyter Berlin, New York $1994$, 1202 p. ISBN 0-89925-4547-8.