Separate rigid containers hold equal numbers of moles of He(g), Ne(g), and Ar(g), all at 300 K. Which statement comparing the three gases is correct?

Core Concept

Kinetic molecular theory states that the average kinetic energy of gas particles equals (3/2)kBT, which depends only on Kelvin temperature. At the common temperature of 300 K, helium, neon, and argon therefore carry identical average kinetic energies despite their very different atomic masses. What changes is speed: argon atoms are about ten times heavier than helium atoms, so they travel proportionally slower to keep the product of mass and speed squared equal.