average velocity of molecules versus temperature

Question

if the molecules in 1.0 L of each of the gasses shown below are all moving with the same average velocity, which gas sample is at the third highest temperature?

Cl2

CoCl2

NH3

Kr

the temperature is the same in all of the gas samples

Answer 1

If they are all moving with the same average velocity, and temperature changes, the kinetic energy (KE) must change because KE is a measure of the kelvin temperature.

KE = 1/2 mv² where KE is kinetic energy; m = mass and v = velocity.

Since the problem states that average velocity (v) is constant, the KE (temperature) will depend on the mass.

The greater the mass, the greater the kinetic energy. So, arrange the gases according to molar mass and the one that is the third highest will have the third highest temperature.