Two moles of argon (mono-atomic ideal gas, molar heat capacity at constant volume Cv=23R) undergo a reversible adiabatic expansion in which the temperature falls from 400K to 250K.
(i) Calculate the change in internal energy ΔU of the gas.
(ii) Hence calculate the work done by the gas during the expansion.
(iii) Comment on the amount of heat exchanged with the surroundings in this process.