Chemistry
Grade-9
Easy
Question
Atmospheric air has 78% N;21; 0.9 % Ar and 0.1 % CO2 via way of means of volume. What is the molecular mass of air within the atmosphere?
- 29
- 25
- 30
- 20
Hint:
Atomic mass of N2 is 28g, O2 is 32g, Ar is 36g, molecular mass of CO2 is 44g.
The correct answer is: 29
Atmospheric air has 78% N;21; 0.9 % Ar and 0.1 % CO2 via way of means of volume.
Atomic mass of N2 is 28g, O2 is 32g, Ar is 36g, molecular mass of CO2 is 44g.
The molecular mass of air within the atmosphere = 0.78
28 + 0.2132 + 0.00936 + 0.00144
= 21.84 + 6.72 + 0.324 + 0.044 = 28.928 
29
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