1. The problem statement, all variables and given/known data A cylinder containing 19 kg of comperessed air at pressure 9.5 times that of the atmosphere is kept in a store at 7 °C. When it is moved to a workshop where the temperature is 27 °C a safety valve on the cylinder operates, releasing some of the air. If the valve allows air to escape when the its pressure exceeds 10 times that of the atmosphere, calculate the mass of air that escapes. Answer: 0.33 kg 2. The attempt at a solution Density of air = 1.293 kg m-3 Mass = Volume * Density VolumeStore = 19 / 1.293 = 14.7 m3 VWorkshop = (pStore * VStore * TWorkshop) / (TStore * pWorkshop) = (9.5 p0 * 14.7 * 300.15) / (280.15 * 10 p0) = 14.95 m3 MassWorkshop = 14.95 * 1.293 = 19.33 kg 19.33 - 19 = 0.33 kg... fits the answer but why the mass is 19.33 after the escape? What's wrong?