A ballon has 5.0 g mole of helium at `7^(@)C` Calculate
(a) the number of atoms of helium in the balloon,
(b) the total internal energy of the system.

Explanation

Given, `n=5.0,T=7^(@)C=7+273=280K`
Number of atoms `=nN_(A)=6.02xx10^(23)=30xx10^(23)`
Average kinetic energy per molecule `=(3)/(2)kT`
`therefore` Total internal energy `=(3)/(2)kTxxN`
`=(3)/(2)xx1.3.8xx10^(23)xx28030xx10^(23)`
`=(3)/(2)xx30xx280xx1.38=1.74xx10^(4)J`