00:02
Hi there.
00:02
In this question, we are working with a gas sample, and we want to work, we're working, we want to know the molar mass, and we're working with density, pressure, and temperature.
00:12
Well, what i'm going to do is i'm going to start off with the ideal gas law.
00:16
That is pv equals nrt.
00:21
And what i'm going to do is i'm going to multiply both sides by the mass of the sample.
00:29
Since i'm multiplying both sides by it, we don't need to know what that mass is.
00:35
And then what i'm going to do is to divide both sides by n and v.
00:44
You'll see why that is in a moment.
00:47
Okay, so let's see.
00:50
N will can't, i'm sorry, not n, v will cancel here on the left.
00:55
And look what we have here.
00:57
We have grams per mole, which is molar mass.
01:00
So i'm going to give molar mass the capital letter m.
01:04
So that's molar mass.
01:06
We still have p there, which is pressure.
01:09
On the right side, the number of moles will cancel, leaving us with r and t, and then we have mass over volume.
01:20
Mass per volume, grams per liter, is density.
01:26
Okay, so i have taken the ideal gas law, and i have derived a related equation that uses molar mass and density.
01:35
And what we're trying to find is the molar mass.
01:38
I'm going to go ahead and divide both sides by pressure.
01:41
So this gives us universal gas constant multiplied by the temperature in kelvin times the density over the pressure is going to give us the molar mass.
01:53
All right.
01:54
So universal gas constant, 0 .0821 is the one i'm going to use because that is the one with atmospheres in it.
02:05
And atmospheres is what we're given our pressure in.
02:09
Temperature...