Answer
You disagree with your friend. On average, hydrogen molecules move faster than nitrogen molecules at the same temperature.
Work Step by Step
They are mixed, which means they have the same temperature. This means they have the same average translational kinetic energy per molecule. $KE = \frac{1}{2} mv^{2}$. The mass m of a hydrogen molecule is much less than that of a nitrogen molecule, so the speed v must be greater to have the same average kinetic energy.
