Question

The number of molecules per unit volume in the sample is 20. The mass of each molecule is 10^-20kg. The mean of speed squared is 4m^2/s^2. What is the value of internal energy of the gas? Assume volume of container is 0.02m^3.

(a) 0.8*10^-20J

(b) 0.53*10^-20J

(c) 0.01*10^-20J

(d) 0.45*10^-20J

The question was posed to me during an interview for a job.

This interesting question is from Kinetic Theory of an Ideal Gas in portion Kinetic Theory of Physics – Class 11

Answer 1

Correct answer is (a) 0.8*10^-20J

The explanation: Internal energy is given by: E = (1/2)Nmv^2,

where N is the total number of molecules = nV.

E = 0.5*20*0.02*10^-20*4

= 0.8*10^-20J.