Physics - Heat & Thermo Question with Solution | TestHub

Average momentum per molecule is zero for both. Both are diatomic at the same temperature, so average KE per molecule $=\frac{5}{2}kT$ is the same. At N.T.P. both have the same number density, so KE per unit volume $=\frac{5}{2}nkT$ is also the same. KE per unit mass differs because the molar masses differ.