Violia, a South Africa design, manufacture, testing and supply company has been asked to design an air vessel that can store air. A Chemical Engineering student from Unisa has been hired to test the vessel's capacity to withstand changes in temperature and pressure. The student has been given a vessel of capacity 12.3m3 which contains air at a pressure of 180kPa and a temperature of 42C. The vessel's pressure and temperature are reduced to 75kPa and 13C, respectively, by removing some air. The student needs to find the amount of air removed and the volume of this mass of air at the initial state of air. Take R=0.287kJ/kg.K for air