1. The problem statement, all variables and given/known data An ideal gas with Cv = 5/2R, and γ = 1.4 starts at a volume of 1.5m3 , a pressure of 2.0×105Pa, and a temperature of 300K. It undergoes an isobaric expansion until the volume is V , then undergoes an adiabatic expansion until the volume is 6.0m3 , and finally undergoes an isothermal contraction until it reaches the original state. 2. Relevant equations What is the volume V of the gas before the start of the adiabatic expansion? 3. The attempt at a solution The answer is 2.23m^3 but I am unsure of how to go about getting it. I tried PV=nRT but I do not know 'n'.