00:01
To calculate the molar mass or molecular weight of air, we do a calculation similar to what we do to calculate the average atomic mass of an element based upon natural abundance and isotopic masses.
00:16
We take the percentage expressed as a fraction, so 78 % is represented as 0 .78.
00:24
We multiply it by the molar mass of the component of air that makes up 78%.
00:31
That is nitrogen.
00:33
We then add to that, 21%, or 0 .21, multiplied by the molar mass of 02, and then 1%, or 0 .01 is a fraction, multiplied by the molar mass of argon.
00:52
And this gives us to two significant figures, because that's all we're going to have when we multiply these two together, will be limited to the 1's position, 29 grams per mole.
01:02
Or as a molecule, a molecular weight would be 21 amu...