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

Here, `mu = 5.0 g "mole" , T=7^(@)C = (7+273)K= 280 K`
Number of He atoms =`mu N = 5.0 xx 6.023 xx 10^(23)`
`N' = 30.115 xx 10^(23)`
As average kinetic energy per molecule = `3/2 kT`
`:.` Total internal energy = `3/2 kT xx N' = 3/2 xx (1.38 xx 10^(-23)) xx 280 xx 30.115 xx 10^(23) = 1.74 xx 10^(4)J`.