The mass of a gas molecule can be computed form the specific heat at constant volume. `Cv` for argon is `0.15 Kcal//kg-k`. The molecular weight of an argon atom is (approximately) `(R = 2 cal//mol-K)`

Options

A. `5 xx 10^(-3) kg`
B. `2.5 xx 10^(-3) kg`
C. `40 xx 10^(-3) kg`
D. `20 xx 10^(-3) kg`

Answer

D

Explanation

`C_(v) = (3)/(2) R - J//mol. K = (3)/(2) (R )/(M) J//kg . K = (3R)/(2M xx 4.2) cal//kgK = 0.15 Kcal//kgK`
`M = (3R)/(2 xx 4.2 xx 0.15 xx 10^(3)) = (3 xx (25)/(3))/(2 xx 4.2 xx 0.15 xx 10^(3)) =20 xx 10^(-3) kg`