How Much Oxygen Does a Medical Cylinder Hold at Different Pressures?

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The discussion focuses on calculating the mass and volume of oxygen in a medical cylinder under high pressure. The cylinder, with a pressure of 140 atm and a volume calculated using its dimensions, initially yields a mass of 0.00394 kg of oxygen. However, the expected answer is 6.4 kg, indicating a miscalculation. Key points include the importance of using the ideal gas law and considering the density of gases, which varies with pressure and temperature. The conversation emphasizes the need to reassess calculations and units for accuracy.
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Homework Statement



An oxygen cylinder for medical use contains oxygen at a pressure of 140 atm, at room temperature (20\circC). 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?


Homework Equations



ideal-gas law pV=nRT
pV=NkT



The Attempt at a Solution



Vcylinder= ∏r2h=(∏)(10 cm)2(110 cm)=3.45 cm3

moxygen= 3.45 cm3 X 1.141 g\bulletcm3=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?
 
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Take care of the units, and recalculate the volume.
How did you get the mass? Note that the density of gases depend on pressure and temperature.

ehild
 

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