Molecular speeds: A container is filled with a mixture of helium (light molecules) and oxygen (heavy molecules) gases. A thermometer in the container reads 22°C. Which gas molecules have the greater average kinetic energy?
A) It is the same for both of the gases because the temperatures are the same.
B) The oxygen molecules do because they are diatomic.
C) The oxygen molecules do because they are more massive.
D) The helium molecules do because they are less massive.
E) The helium molecules do because they are monatomic.

Question

Quizplus · Accepted Answer

The average kinetic energy of gas molecules in a mixture is determined by the temperature of the system, not by the mass or molecular structure of the gases. Since both helium and oxygen gases are at the same temperature (22°C), they have the same average kinetic energy.

Molecular Speeds: a Container Is Filled with a Mixture of Helium