Physics- pv=nRt; What am I doing wrong?

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Homework Statement


In a portable oxygen system, the oxygen (O2) is contained in a cylinder whose volume is 0.0029 m3. A full cylinder has an absolute pressure of 1 107 Pa when the temperature is 290 K. Find the mass of oxygen in the cylinder.



Homework Equations


pv=nRt


The Attempt at a Solution


I used pv=nRt to get-----> (1E7)(.0029)=n(8.31)(290) and I solved for "n" and got n=12.03. Then i multiplied 12.03 by 16 (the mass of oxygen from the periodic table) to get mass from moles. This gave me 192.54 grams. But my answer had to be in kg, so i got .1925. But, my online hw keeps marking that wrong? Can you tell me if I made a mistake anywhere along the way? I am very confused about this.
 

Answers and Replies

  • #2
Borek
Mentor
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3,078
Your molar mass of oxygen is wrong. 16 is molar mass of just O.
 
  • #3
146
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oh i see now. thanks for your assistance
 

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