1. The problem statement, all variables and given/known data A vessel of capacity 3m^3 contains air at a pressure of 1.5 bar and a temperature of 25 celcius. Additional air is now pumped into the system until the pressure rises to 30 bar and temperature rises to 60 celcius. Determine the mass of air and express the quantity as a volume at a pressure of 1.02 bar and a temperature of 20 celcius. If the vessel is allowed to cooled until the temperature is again 25 celcius, calculate the pressure in the vessel. 2. Relevant equations 3. The attempt at a solution I do not really know how to start to solve this question. Thanks in advance to those who can help me. Does the additional air pumped in considered as the heat pumped in? Furthermore, should I consider whether the system is closed or opened firstly?