Air

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Air is hopefully self-explanatory. It is one of the most basic and essential words in any language. The speed of sound in dry air at 20°C and 1atm is 343m/s.

Composition

Components of air
1 liter 1 m3
moles grams moles grams
1atm, 20°C, 0% humidity
Nitrogen ({{#Chem: N2}}) 0.0324 0.9072 32.4 907.2
Oxygen ({{#Chem: O2}}) 0.0087 0.2784 8.7 278.4
Argon ({{#Chem: Ar}}) 0.0004 0.016 0.3984 16
Carbon Dioxide ({{#Chem: CO2}}) 0.0000166 0.0007304 0.0166 0.7304
Check(sum) 0.0415✓ 1.2017✓ 41.515✓ 1201.7✓
1 atm, 20°C, 100% humidity
Water ({{#Chem: H2O}}) 0.0009 0.0162 0.9 16.2

Air is composed of 78% nitrogen, 21% oxygen, 0.96% argon and 0.04% carbon dioxide.

  • Volume of 1 mol of a gas at 20°C: 24.05L
    PV = nRT
    V = nRT
    P
    P = 1 (atm)
    n = 1 (mol)
    R = 0.082057 (L atm K−1 mol-1) ideal gas constant
    = 0.082057T
    = 0.082057×293 = 24.042701
  • Molar mass of air: 28.9776g/mol
    = 0.78 * 28 + 0.21 * 32 + 0.01 * 40 + 0.0004 * 44
    = 21.84 + 6.72 + 0.4 + .0176
    = 28.9776
  • Density of air: 1.20488 g/L (20°C, 1atm)
    Density = g
    L
    (water = 1000)
    = 28.9776g/mol
    24.05L/mol
    = 1.20488g/L at 20°C
  • How many liters of air at 20°C represents 1mol of {{#Chem: O2}}? 127L
    1 mol of {{#Chem: O2}} weighs 32g (2x molar weight of oxygen)
    Air is 21% {{#Chem: O2}} by mass
    32g / 0.21 = 152g of air contains 32g (1 mol) of {{#Chem: O2}}
    152g
    1.2g/L
    = 127L of air at 20°C contains 1mol of {{#Chem: O2}}
  • Inversely, How many mol of {{#Chem: O2}} are in 1L of air? .0079
    1/127 = .0079


See Also

References

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