00:01
Okay, what we want to do is step through the process of being able to determine the molecular formula for a substance called equilene.
00:10
We are starting with 13 .42 grams of equilene, which contains only carbon, oxygen, and hydrogen.
00:19
And when combust it produces 39 .61 grams of co2 gas and 9 .01 grams of water vapor.
00:28
And we're told that the molar mass of equilene is 268 .3, 4 grams per mole.
00:37
Okay, so what we first need to do is we need to actually find the mass of, so kind of like the first step is to find the mass of carbon and hydrogen, given the gases of co2 and hg.
00:58
So we're going to find the molar mass.
01:03
So we're going to find the molar mass of carbon dioxide and the molar mass of h2o.
01:11
Okay.
01:12
So depending on what periodic table you have, we have one carbon.
01:19
So that is 12 .01.
01:23
And we have two times oxygen, which is 16 .00.
01:28
Okay.
01:32
We're going to add those together, and we should get 44 .01 grams per mole of co2.
01:51
So that's the molar mass.
01:54
And now we're going to do the same thing for h2o.
01:58
So we have two hydrogen, so we do two times 1 .01.
02:05
Now some of your periodic tables we might have this as 1 .008 depending on your periodic table.
02:14
Go with the periodic table you have.
02:17
Sometimes oxygen is 15 .999 if it goes down to three decimal places.
02:22
And then of course we have 16 here.
02:26
And we add those together.
02:29
And we get 18 .02 grams per mole for the molar mass of h2o.
02:39
Okay.
02:42
For, now if we want to do the mass of carbon, so for in co2, we have one mole of carbon and one mole of co2.
03:00
So what we have is we are starting with 39 .6 grams of co2.
03:15
We're going to change to, moles.
03:18
So we have one mole of co2 for 44 .04 .0 1 .01 grams of co2.
03:32
We have one mole of carbon for one mole of co2.
03:45
And we know that carbon is 12 .01 grams of carbon for one mole of carbon.
03:58
Okay.
03:59
So let's see if our units cancel out.
04:01
So grams of co2, mole of co2, mole of carbon, mole of carbon, and we're left with grams of carbon.
04:11
So that's how we find the mass of carbon.
04:14
And so the mass of carbon is 10 .81 grams.
04:21
And we're going to do the exact same thing for hydrogen.
04:27
Okay, so we're going to find the mass of hydrogen.
04:33
And so in water we have two moles of hydrogen for one mole of, so we're looking at the coefficient and the subscript.
04:43
So one mole of h2o contains two moles of hydrogen.
04:49
So for the mass of hydrogen, we're starting with 9 .01 grams of h2o.
04:58
And we're going to kind of do the exact same thing we just did with carbon, okay? and so we know there's one mole of h2o to 18 .02 grams of h2o.
05:19
We have two moles of hydrogen for one mole of h2o.
05:32
And we have 1 .01 grams of hydrogen for one mole of hydrogen.
05:38
Okay.
05:43
And so we should get 1 .01 grams of hydrogen.
05:51
Okay, so that's the mass.
05:55
Okay.
05:56
And then we could do a couple things to find the mass of oxygen.
06:07
So we know that for the mass of equilene is 13 .4.
06:18
4 to grams.
06:21
Well, that total mass of equylene should be the masses of each of hydrogen, carbon, and oxygen added together.
06:31
So that might be the easiest way to do this.
06:34
So the mass of carbon plus the mass of hydrogen plus the mass of oxygen plus the mass of oxygen should equal the mass of oxygen.
06:55
Equalene.
06:57
Okay.
06:58
So i basically have the mass of oxygen equal to, we were told this was 13 .42 grams of equaline minus the mass of carbon, which is 10 .81, minus 1 .01 grams of hydrogen.
07:27
And that should give us what is left over for oxygen in that total amount.
07:33
And so we get 1 .60 grams of oxygen...