These two questions go together, so thank you for answering them both. I really need 5, but I can't post 5 alone as a question, it would make no sense. ANYWAY - The Callen book solutions given are incomplete/wrong. 4 needs the INITIAL and FINAL pressures and final volume and ALL answers already posted on Chegg have different solutions!!! Eeek. 5 the work done needs to match the difference in energies. In Chegg's solutions they do not. Please help me understand this problem. Thank you!

4. Two moles of a monoatomic ideal gas are at a temperature of 0C and a volume of 45 liters. The gas is expanded adiabatically (Q = 0) and quasi-statically until its temperature falls to -50C. What are its initial and final pressures and its final volume? (Callen, Problem 3.4-3) Goal: Find the Pi, P and Vf. Recall: = (a) The differential of internal energy d can be expressed in two ways. i. dU = CydT ii. d =W +Q (b) Temperature and volume relation for an adiabatic process (Q = 0) for an ideal gas (3) (4) CydT CNR dT T Tf cin T -PdV NR - d V Vi -In V. = (5) c (6) () (6) T 5. By carrying out integral PDV, compute the work done by the gas in Problem 3.4-3. Also compute the initial and final energies, and corroborate that the difference in these energies is the work done. (Callen, Problem 3.4-4)