- #1
FaraDazed
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Homework Statement
Part A: Calculate how many mocules per cubic metre in air at 27°C and at a pressure of 1.1 atm (1atm is 1.01 x 10^5)
Part B: What is mass in grams of 2.4m^3 of this air.
Assume that 75% of the air is N2 (with molar mass of 28 g/mol) and 25% O2 (with molar mass of 32 g/mol)
Homework Equations
[itex]PV=nRT[/itex]
The Attempt at a Solution
Using the equation above, I solved for n, which I took it to mean the number of moles of air.
[itex]
n=\frac{PV}{RT}=\frac{(1.1 \times 1.01 \times 10^5)(1)}{8.315 \times (273.15 + 27)} = 44.515
[/itex]
So then to work out for Nitrogen I found 75% of 44.515, which is 33.39 then multipled that by avagaros number to get the number of atoms, then divided by 2 to get the number of N2 molecules.
[itex]
(44.515)(0.75)=33.39 \\
33.39 \times 6.02 \times 10^{23} = 2.01 \times 10^{25} \,\,\, atoms \\
2.01 \times 10^{25} \times 0.5 =1.004 \times 10^{25} ,\,\,\ molecules
[/itex]
Then did exactly the same process but for oxygen, using 44.515*0.25 and got a number of 3.35 x 10^24 molecules of O2.
Then for Part B:
I multiplied the number of N2 molecules in 1m^3 by 2.4 to get how many there would be in 2.4m^3, and then multiplied that by 28u to get the weight in Kg. Did the same process for the oxygen, and then added them together.
For N2
[itex]
(1.004 \times 10^{25})(2.4)=2.4096 \times 10^{25} \,\,\, molecules \\
(2.4096 \times 10^{25})(28 \times 1.66 \times 10^{-27})=1.12 kg
[/itex]
For O2
[itex]
(3.3498 \times 10^{24})(2.4) = 8.3952 \times 10^{24} \,\,\,\, molecules \\
(8.3952 \times 10^{24})(32 \times 1.66 \times 10^{-27}) = 0.45 kg
[/itex]
Therefore total mass in 2.4m^3 in grams
[itex]
1120+450 = 1570g
[/itex]