Oxygen molecules are 16 times more massive than hydrogen molecules. At a given temperature, how do their average molecular speeds compare? The oxygen molecules are moving
A) four times faster than the hydrogen molecules.
B) at 1/4 the speed of the hydrogen molecules.
C) at 1/16 the speed of the hydrogen molecules.
D) sixteen times faster than the hydrogen molecules.
E) at $1 / \sqrt { 2 }$ the speed of the hydrogen molecules.

Question

Oxygen molecules are 16 times more massive than hydrogen molecules. At a given temperature, how do their average molecular speeds compare? The oxygen molecules are moving 
A) four times faster than the hydrogen molecules.
B) at  1/4  the speed of the hydrogen molecules.
C) at  1/16  the speed of the hydrogen molecules.
D) sixteen times faster than the hydrogen molecules.
E) at $1 / \sqrt { 2 }$ the speed of the hydrogen molecules.

Quizplus · Accepted Answer

The average speed of molecules in a gas is inversely proportional to the square root of their mass (according to the kinetic theory of gases). Since oxygen molecules are 16 times more massive than hydrogen molecules, their average speed will be $\sqrt{16} = 4$ times slower, not faster, than that of hydrogen molecules.

Oxygen Molecules Are 16 Times More Massive Than Hydrogen Molecules 1/21 / \sqrt { 2 }1/2​

Oxygen Molecules Are 16 Times More Massive Than Hydrogen Molecules $1 / \sqrt { 2 }$