1. The problem statement, all variables and given/known data Argon is a monatomic gas for which all the internal energy of the molecules may be considered to be translational kinetic energy. Molar mass of argon = 4.0 x 10-2 kg. The Boltzmann constant = 1.38 x 10-23 J kg-1 . The Avogadro constant = 6.02 x 1023 mol-1 . Calculate the internal energy of 8.0 g of argon gas at a temperature of 100 K. 2. Relevant equations pV=nRT or pV=NKT U=3/2NKT 3. The attempt at a solution So far I'm assuming you need U=3/2NKT We know that 1 mol = 4x10^-2 Kg So i did 0.008/4x10^2 = 0.2 0.2 x Avagardo's Constant = 1.204x10^23 And subbed that into U=3/2NKT as N The final answer I got was as U was 248.4J To be honest i have no clue what I did as its been so long since I've done Physics. Thanks for any help or any pointers in the right direction.