How do you find the mass of air in grams of a room with knowing nothing except for the volume of the room?

Question

How do you find the mass of air in grams of a room with knowing nothing except for the volume of the room?

Answer 1

You would then estimate the density of the air in the room (approximately 1.2 grams per centimeter at sea level) and then compute mass as the product ot that density and the volume.

Answer 2

At least two ways, for each of which you must know one other thing.

a). Density of air at the temperature and air pressure of the room. At sea level and at 20 °C, air has a density of approximately 1.2 kg/m3. You can correct this number to whatever conditions you have by using the laws of Boyle and Charles.

b). Molar volume of an ideal gas at STP is 22.414 L/mole. Correct this number to the actual conditions using the gas laws as above and multiply by the volume of the room, remembering to keep your units straight. Now you have the number of moles of air in the room. Since air is essentially 80% N2 and 20% O2, you can figure that air has an average molar mass of:

(0.8x 28) + (0.2 x 32) =  28.8

{The mean molar mass of air is actually 28.97g/mol because air contains a small amount of other gases - Ar, CO2, H2O}

Multiply 28.8 by the number of moles you just calculated and again you have a value for the mass of air in the room.    

Answer 3

According to the CRC Handbook of Chemistry and Physics, the density of dry air at 20 degrees C at 760 mm of mercury (one atmosphere of pressure) is 1.204 milligrams per cubic centimeter.

1 cubic foot = 28,316.8467 cubic centimeters.

So, dry air weighs 34,093.48 mg per cu.ft.

Which is about 1.2 ounces per cu.ft.