1. The problem statement, all variables and given/known data This question is to due with a compressor experiment. I've actually posted 2/3 questions on this write up in the past 2 days. Anyway, a compressor takes air from the atmosphere and compresses it before forcing it into a receiver volume. You are asked to calculate the mass of air that is initially in the receiver, the final mass in the receiver and subsequently the mass that has been transferred in. You are given the atmospheric conditions P0 and T0 as well as the final conditions PF and TF. The volume of the receiver is also given. Also n, the polytropic exponent was found to be ≈ 1 (1.014 to be exact). Finally, you are asked to find the volume that the transferred mass of gas occupies at atmospheric conditions using P1V1n = P2V2n = PVn 2. Relevant equations Given equations: P1V1n = P2V2n = PVn PV = mRT. 3. The attempt at a solution PV = mRT. m = PV/RT. minitial = P0V/RT0. mfinal = PFV/RTF. mtransferred = mfinal - minitial. Correct so far? This is where I get a little stuck. You are told to use P1V1n = P2V2n = PVn to calculate the volume that mtransferred will occupy at P0 and T0. Why is it not ok to use PV = mRT for this question? Subbing mtransferred, P0 and T0 into the ideal gas law and solving for V. I've actually asked the lecturer why this is and he told me that the ideal gas law could be used but it's use will be a little more involved. Anybody have any ideas where I may be going wrong? And how I could actually use P1V1n = P2V2n = PVn to solve for the volume occupied at atmospheric temp and pressure?