Which molecule moves with the fastest average speed in Earth's atmosphere in thermal equilibrium?
A) water (atomic mass = 18)
B) carbon dioxide (atomic mass = 44)
C) nitrogen (atomic mass = 28)
D) oxygen (atomic mass = 32)

Question

Quizplus · Accepted Answer

The rate of thermal motion of a molecule is determined by its mass and temperature. The lower the mass, the higher the average speed of the molecule at a given temperature. Therefore, given the same temperature, molecules with lower atomic mass will have higher average speeds than those with higher atomic mass. Water has the lowest atomic mass among the given choices, making it the molecule with the highest average speed in Earth's atmosphere in thermal equilibrium.

Which Molecule Moves with the Fastest Average Speed in Earth's