00:03
Hi there, in this question we are trying to find a molar mass, and we know that molar mass is defined as mass in grams per mole of the substance.
00:18
Okay, so we're trying to find mass over moles.
00:23
Well, we're given the mass, we're told it is 1 .15 gram sample, but it is the moles that we are lacking here.
00:33
Fortunately, we have enough information that we can use the ideal gas law to solve for moles.
00:38
The ideal gas law equation is pv equals nrt.
00:43
We're arranging this to solve for the number of moles.
00:48
We'll divide both sides by rt, and we see then that the number of moles is equal to pv over rt.
01:00
Sounds simple enough.
01:02
Let's go ahead and put in our values.
01:05
P represents pressure.
01:07
The pressure here is 572 millimeters of mercury.
01:13
The v represents volume.
01:19
We're told that we have 0 .856 liters.
01:27
R represents the universal gas constant.
01:30
We want to use the one that has millimeters of mercury in it, and that is 62 .36 liters times millimeters of mercury over mole times kelvin.
01:43
So rather unique units, but after all it is a constant, so they frequently have interesting combinations of units...