What is the average kinetic energy of the molecules in a gas at 273K?

The average kinetic energy of the molecules is 5.66 × 10⁻²¹ J.

According to Kinetic Molecular Theory, the average kinetic energy of gas molecules is a function only of temperature.

The formula is

##KE = 3/2kT##

where ##T## is the Kelvin temperature and ##k## is Boltzmann's constant.

##KE = 3/2 × 1.381 × 10⁻²³ "J·K⁻¹" × 273"K"## = 5.66 × 10⁻²¹ J

For a mole of molecules, the average kinetic energy is

##(5.66 × 10⁻²¹"J")/(1"molecule") × (6.022 × 10²³"molecules")/(1"mol")## = 3.41 ×10³ J/mol = 3.41 kJ/mol