The mass of a gas molecule can be computed form the specific heat at constant volume. Take `C_(V) = 0.075 kcal kg^(-1) k^(-1)` for argon and calculate
a. the mass of an argon atom
b. the atomic weight of argon.

Options

A. `40 kg`
B. `40 xx 10^(-3) kg`
C. `20 kg`
D. `20 xx 10^(-3) kg`

Answer

B

Explanation

b. `C_(v) = (3R)/(2) J//mol K = (3 R)/(2 M) J//kg K`
`= (3R)/(2M xx 4.2) cal//kg K = 0.075 kcal//kg K`
Molecular weight of argon atom
`M = (3R)/(2 M xx 4.2 xx 0.075 xx 10^(3))`
`= (3 xx (25)/(3))/(2 xx 4.2 xx 75) = 40 xx 10^(-3) kg`