The internal energy of one geam of helium at 100 K and one atmospheric pressure is

Options

A. 100 J
B. 1200 J
C. 300 J
D. 500 J

Answer

C

Explanation

The helium molecule is monatomic and hence its internal energy per molecule is `(3)/(2)k_(B)T`. (where `k_(B)` is the Boltzmann constant). The internal energy per mole is therefore is `(3)/(2)RT`. One gram of helium is one fourth mole and hence its internal energy is `(1)/(4)xx(3)/(2)Rxx100=300J`, taking the value of R to be approximately 8 J `mol^(-1)K^(-1)`.