A tank used for filling helium balloons has a volume of `0 .3 m^3` and contains (2.0) mol of helium gas at `20 .0^@ C`. Assuming that the helium behaves like an ideal gas.
(a) What is the total translational kinetic energy of the molecules of the gas ?
(b) What is the average kinetic energy per molecule ?

Explanation

Using `(KE)_(trans)=3/2nRT`
Given `n=2.0` mol and `T=293 K`
`therefore (KE)_(av)=3/2(2.0)(8.31)(293)=7.3xx10^(3)J`
The average kinetic energy per molecule is `3/2kT.`
`(KE)_(av)=3/2kT=3/2(1.38xx10^(-23))(293)`
`=6.07xx10^(_21) J`