Ideal Gas Law

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  • #1
physicsss
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A standard cylinder of oxygen used in a hospital has the following characteristics at room temperature (300 K): gauge pressure = 2500 kPa, volume = 10 liters. How long will the cylinder last if the flow rate, measured at atmospheric pressure, is constant at 2.4 liters/min?

I'm lost on this one...how do I relate flow rate to the Ideal Gas Law?
 

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  • #2
HallsofIvy
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PV= nRT so that Volume is inversely propotional to pressure. What is "atmospheric pressure" in terms of kPa and what would the volume be at that pressure?
 
  • #3
LeonhardEuler
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If the flow rate is 2.4L/min, how many moles per minute is that? Remember, it is 2.4 L at 1atm and 300 K every minute. You can use the ideal gas law to find the total # of moles of gas in the tank to begin with. You can probably figure it out from there.
 
  • #4
HallsofIvy
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I don't see why you would need to calculate moles. You are given volume (at 2500 kPa) and that at atmospheric pressure, 2.4 liters/min come out. Use PV= nRT (where nRT is constant) to determine the number of liters at atmospheric pressure and divide by 2.4 liters/min.
 
  • #5
LeonhardEuler
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That's true. It's more logically straightfoward to me to calculate the actual amount of stuff coming out of the tank and compare that to the total amount of stuff in the tank, but your method involves less calculation. It's a matter of personal preference I guess.
 

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