1. The problem statement, all variables and given/known data An oxygen cylinder for medical use contains oxygen at a pressure of 140 atm, at room temperature (20[itex]\circ[/itex]C). The cylinder measures 20 cm in diameter and 110 cm in length. How many kilograms of oxygen does this cylinder contain? What will be the volume of the oxygen if it is allowed to expand slowly to normal atmospheric pressure, at room temperature? 2. Relevant equations ideal-gas law pV=nRT pV=NkT 3. The attempt at a solution Vcylinder= ∏r2h=(∏)(10 cm)2(110 cm)=3.45 cm3 moxygen= 3.45 cm3 X 1.141 g[itex]\bullet[/itex]cm3=3.94 g or 0.00394 kg According to the book the answer to this part is 6.4 kg What did I do wrong?