Number of oxygen molecules in our lecture theatre

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SUMMARY

The discussion centers on estimating the number of oxygen molecules in a lecture theatre with a volume of approximately 200 m³ under standard conditions. Using the ideal gas law, PV=nRT, the calculated number of moles of gas is approximately 8922.997, leading to an estimation of around 1900 moles of oxygen in the room. Given that oxygen constitutes 20.95% of air, the total number of oxygen molecules is derived by multiplying the moles of oxygen by Avogadro's number. This straightforward calculation confirms the presence of a significant quantity of oxygen in the lecture theatre.

PREREQUISITES
  • Understanding of the ideal gas law (PV=nRT)
  • Familiarity with Avogadro's number (6.022 x 10²³ molecules/mol)
  • Basic knowledge of gas properties under standard temperature and pressure (STP)
  • Ability to perform unit conversions and calculations involving percentages
NEXT STEPS
  • Study the implications of gas laws in real-world applications, focusing on PV=nRT
  • Explore the concept of Avogadro's number and its significance in chemistry
  • Investigate the composition of air and the role of different gases in various environments
  • Learn about standard temperature and pressure (STP) and its relevance in gas calculations
USEFUL FOR

Students in chemistry or physics, educators teaching gas laws, and anyone interested in atmospheric science or environmental studies.

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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