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
Messages
7
Reaction score
0
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)
 
Physics news on Phys.org
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!
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Mean distance between air molecules
Replies
10
Views
5K
Finding the mass of a quantity of gas given P, V, T
Replies
5
Views
2K
Deducing Number of Molecules in a Scuba Tank
Replies
2
Views
4K
Clarification on PV=nRT question.
Replies
6
Views
2K
Calculating Number of O2 and N2 molecules per m^3 of air
Replies
8
Views
7K
Mixture of hydrogen and oxygen in container
Replies
27
Views
4K
Calculating Pressure & Density Proportions with Changing Altitude & Temperature
Replies
19
Views
2K
Getting moles number of Oxygen in Balloon - 65 characters
Replies
6
Views
2K
Calculating Oxygen Mass in a Portable Cylinder | Physics Homework Help
Replies
2
Views
4K
Ideal Gas Law Homework: Calculating Number Density and Spacing Between Molecules
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top