Part A: What mass of carbon dioxide is present in 1.00 m3 of dry air at a temper
ID: 934006 • Letter: P
Question
Part A: What mass of carbon dioxide is present in 1.00 m3 of dry air at a temperature of 19?C and a pressure of 651torr? Express your answer with the appropriate units.
Part B: Calculate the mass percentage of oxygen in dry air. Express your answer with the appropriate units.
If you could explain how you got your answer that would be great! Thank you!
Here is given info:
Air is a mixture of several gases. The 10 most abundant of these gases are listed here along with their mole fractions and molar masses.
Component Mole fraction Molar mass(g/mol) Nitrogen 0.78084 28.013 Oxygen 0.20948 31.998 Argon 0.00934 39.948 Carbon dioxide 0.000375 44.0099 Neon 0.00001818 20.183 Helium 0.00000524 4.003 Methane 0.000002 16.043 Krypton 0.00000114 83.80 Hydrogen 0.0000005 2.0159 Nitrous oxide 0.0000005 44.0128
Explanation / Answer
Part A
These are the proportions
Nitrogen - 78.09 % - Oxygen - 20.95% - Argon - .93% - - Carbon Dioxide - .03% Methane -.04% Neon - .0018% - Helium - .0005% Krypton - .0001% - Hydrogen Nitrous Oxide - negligible amount
You get the atomic weights of the above and then the number of moles and work out with the percentages.
atomic/molecular weights:
O2 32.00
N2 28.02
CO2: 44.01
H2: 2.02
Ar2 39.04
Ne2 21.08
He2 4.00
K 83.8
You only need to consider O2 N2 CO2 and Ar2 as the others are trace amouts.
kg/kmol:
O2 32.00
N2 28.02
CO2: 44.01
Ar2 39.04
fraction of gases:
02 0.2095
N2 0.7809
CO2 0.0003
Ar2 0.0093
Molecular mass
02 6.704
N2 21.88
CO2 0.013
Ar2 0.373
Total = 28.97
? = p / (R T)
where
p = pressure (kPa)
R = 286.9 = individual gas constant (J/kg degK)
T = absolute temperature (degK)
pressure 675 torr = 89.993 kPa and T = 273 + 23 = 296 degK
? = (89.993 kPa) / ((286.9 J/kg degK) (296 degK))
= 1.0597 kg/m3 air
(0.013/28.97)*1.0597 = 0.0004755 kg in 1.00 m^3 = 0.4755 grams per 1.00 m^3
Part B
23.1%
add up the first few (Mole fraction x Molar Mass), you'll see the molar mass of dry air is ~29
divide oxygen's (Mole fraction x Molar Mass) / 29 and you'll get .231135...
so, to 3 sig figs: oxygen is 23.1% by mass in dry air
Source(s):I did this problem in Mastering Chemistry and got the correct answer