Number of oxygen molecules in our lecture theatre

AI Thread Summary
The discussion focuses on estimating the number of oxygen molecules in a lecture theatre with a volume of approximately 200 m^3 under standard conditions. Using the ideal gas law (PV=nRT), the calculation yields about 8923 moles of gas, with oxygen making up 20.95% of the air. This results in approximately 1900 moles of oxygen, which translates to a significantly larger number of molecules when multiplied by Avogadro's number. Participants clarify the calculations and confirm the initial confusion regarding the numbers. The conversation highlights the importance of proper calculations in determining gas quantities in enclosed spaces.
Chewy247
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1. Estimate the number of oxygen molecules in LTD under normal pressure and temperature.



2. I'm guessing you use PV=nRT to get the number of moles of gas in the room and work out the % of oxygen in the air, but I got a number which to me looks too small.



3. Volume of LTD is approx 200m^3, P=101325 Pa, R=8.314472 J K-1 mol-1, T=273.15 K.

n=8922.996613.
20.95% of air is oxygen, therefore I wound up with 1869.36779 molecules of oxygen in the room.

(See I can't tell if there is more to it, or if the holidays have turned me into a thoroughbred moron)
 
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No, you ended up with ~1900 moles of oxygen in the air. You'd then have 1900*Avagadro's # molecules of oxygen.
 
Heheh I knew it was that simple. It seems I have a bit of mind fuzz, thanks for the kick in the arse!
 
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