How do you measure the weight of air in a room??????

Question

I read in my science book that the weight of air in a room is about 70 kg. How was the air in the room measured???
Just wondering.

Answer 1

You could measure the volume of the room multiply this by the density of the air to find the mass of the air.

Density = mass / volume
mass = Density * volume

In order to find the weight of the air once one knows the air's mass, simply multiply by the gravitational acceleration (9.81 m/s^2).
Weight = mass * gravity

At STP (0 degrees C, 1 atm of pressure), dry air has a density of about 1.293 g/L.

Answer 2

As any other stuff, air has a specific gravity, or density. Its exact value depends mainly on height above sea level, although in a lesser degree, it also varies with weather, ambient temperature, and other factors. Anyhow, in SI (metric) units its density is about 1.293 kg/m³, at 0°C and 760 mm Hg. At 20°C, density is near 1.2 kg/m³.

A room measuring 6 m × 4 m × 2.4 m, which is nothing unusual, would indeed hold about 70 kg of air.

Answer 3

Theoretically you could weigh an empty jar, (as in a jar with only vacuum inside), and then fill the jar with a room's worth of air, and see how much mass the jar gained. An easier (as in: 'possible') way is first determining the amount of molecules in the room. To simplify this, we can assume that air is all Nitrogen.

The ideal gas law tells us P V = n R T. We can then solve for the number of moles of nitrogen by n= (P V)/(R T). Standard pressure is 1 atmosphere, and standard temperature is ~300 Kelvin. I'll calculate this for a room which is 15 ft by 15 ft by 8 ft... this is 9000 cubic feet, or using a conversion factor, about 51,000 Liters. Finally, in these units, R isabout 0.082.

Plugging these numbers in, I find 2073 moles of nitrogen. Finally, the molecular weight of nitrogen (remember, nitrogen is diatomic) 28 grams per mole, so the total mass in the room is 2073*28= 58,044 grams, or 58 kilograms. Of course this (and the figure you cited) is the mass of the air; to find its weight, multiply by the acceleration of gravity.

Not the same answer as you saw in your book, but its pretty close considering I don't know what size room it was quoted for! Of course, this is a back of the envelope type of calculation... air isn't really all Nitrogen, or we would all suffocate!

Hope this made sense...

Answer 4

To measure the weight of air "they" (the SI (international standard people) probably used a very accurate scale and set it to zero in a vacuum, or they found the default behaviors of fluids and compared it to on earth.

Answer 5

Mass= Density * Volume of room
Mass = Density * ( Length * Breath * Height)

Weight = Weight * 9.81( gravitational accleration)

This the way to find the weight.. I don't remember the density of air perfectly.

Answer 6

you figure out the area of the room, the density of air in the room and the weight of air, eh?

Answer 7

you can calculate it by using the equation pv=nrt

the air is roughly 80%nitrogen and 20% oxygen

Answer 8

Not directly! BTW, kg is the unit of mass, not weight....

It was calculated by the formula m = ρ*V where ρ is about 1.3 kg/m³.

Answer 9

i supose if you condenced it into a container then you could weight it on a scale.