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 4m2/s2. What is the value of internal energy of the gas? Assume volume of container is 0.02m3.

Correct Answer: 0.8*10-20J
Internal energy is given by: E = (1/2)Nmv2, where N is the total number of molecules = nV. E = 0.5*20*0.02*10-20*4 = 0.8*10-20J.