00:01
So this problem gives us the mass of an empty flask and the mass of a full flask and asks us if the helium that is in that full flask is pure helium or if there's something else in it.
00:14
And so the first thing we want to do is find the actual mass of helium and compare it to the mass of the gas that's in this flask.
00:22
And if those are the same, then it's pure helium.
00:24
And so the first thing we do is the ideal gas law to solve for the number of moles of helium.
00:31
So pv equals nrt is the ideal gas law.
00:35
We have our pressure as 768 tor, which we divide by 760 to convert to atmospheres.
00:42
So we have 1 .01 -053 atmospheres.
00:49
Now we have our volume, which is 118 milliliters.
00:53
We can convert that to liters by just dividing by 1 ,000.
00:56
So we have 0 .118 liters.
01:00
N is our unknown in this case.
01:04
R is a constant 0 .082 -057 liter atmospheres per mole kelvin.
01:16
And our temperature is 35 degrees celsius, which we can convert to kelvin by just adding 273 .15 to get that we have 308...