Helium and argon gases are at the same temperature, 300 K. The ratio of their average kinetic energies per molecule is:
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Question

Helium and argon gases are at the same temperature, 300 K. The ratio of their average kinetic energies per molecule is:

G1 Physics · Accepted Answer

For an ideal monatomic gas, the average translational kinetic energy per molecule is K a v g K_avg K a ​ v g = (3/2)kT. It depends only on temperature, not on molar mass. Since helium and argon are at the same temperature, K H e K_He K H ​ e = K A r . K_Ar. K A ​ r . Therefore, K H e : K A r K_He:K_Ar K H ​ e : K A ​ r = 1:1. Correct option: D.