Physics

Internal energy depends only on temperature for an ideal gas, and it's determined by how many degrees of freedom the molecules have. Hydrogen gas ($\text{H}_2$) is diatomic, so each molecule can move in 3 directions and rotate in 2 independent ways—that's 5 degrees of freedom total. Use the equipartition theorem: each degree of freedom contributes $\frac{1}{2}k_B T$ per molecule, then scale up to 3 moles.

Internal energy depends only on temperature for an ideal gas, and it's determined by how many degrees of freedom the molecules have. Hydrogen gas ($\text{H}_2$) is diatomic, so each molecule can move in 3 directions and rotate in 2 independent ways—that's 5 degrees of freedom total. Use the equipartition theorem: each degree of freedom contributes $\frac{1}{2}k_B T$ per molecule, then scale up to 3 moles.