The major gases that comprise the Earth's atmosphere are shown in Table below. The properties of the gases (ignoring water vapor, which is variable) in the atmosphere remain virtually constant to a high of about 25km.
|
Gas
|
Volume (%)
|
Molecular Weight (approximate)
|
Weight %
|
|
Nitrogen
|
78.000
|
28
|
75.00
|
|
Oxygen
|
21.000
|
32
|
23.00
|
|
Argon
|
00.930
|
40
|
1.3
|
|
Carbon dioxide
|
00.035
|
44
|
0.05
|
|
Average Atmosphere
|
100.000
|
29
|
100.00
|
*Percentages do not add up to 100 due to rounding, approximation, and ignoring water vapor and all minor and trace gases.
*Weight % is found by multiplying the volume (%) by the molecular weight of that gas and dividing by the average molecular weight of the atmosphere.
Weighting the Atmosphere
At sea level, the weight of 1 cm2 of air is approximately 1 kilogram. This value, 1kg/ cm2 is also known as the atmospheric pressure. For this analysis, we will assume a featureless Earth without continents. This will simplify but not significantly alters your calculations.
Question 2: How much does the atmosphere weigh over each square meter of surface? Express this in tonnes (units of 1000 kg). Recall the conversion factors: 104 cm2 = 1m2, 1 tonne = 1000 kg = 106 g.