00:01
Okay, so for this problem, this is similar to others that are in your textbook.
00:07
So this is all about theoretical actual yield and percent yield.
00:12
So as a reminder, percent yield equals actual yield, which will be given to you, divided by theoretical yield, which will be calculated prior to the lab, hopefully.
00:33
This would be what happens if everything goes perfectly well, and you multiply that value by 100 to get the percent.
00:40
So for part a, we're starting with 40 grams of carbon, and we're trying to figure out how much cs2 can be produced because our actual yield is 36 grams of cs2.
01:01
So to start, we've got to take what we know, which is 40 .0 grams of carbon.
01:09
My blue values are all coming from the periodic table.
01:12
So that's the mass off the periodic table, which is 12 .01.
01:18
And that is equivalent to one mole of that substance.
01:22
Then we have to get rid of moles.
01:24
So we put moles on the bottom.
01:26
And we're trying to get to grams of cs2, excuse me.
01:30
So we're going to put mole of cs2.
01:32
Because we can't go straight two grams of an unknown substance.
01:35
So when we have mole on top of mole, we have to look at our coefficients.
01:39
For carbon, it is five for cs.
01:42
It is 1.
01:44
So we're going to have 1, 5.
01:47
And last but not least, we need to convert it to grams.
01:51
So we're going to put mole of cs2 on the bottom, grams of cs2 on the top.
01:57
Grams of cs2 is going to be pulled from the periodic table.
02:01
It ends up being 76 .13.
02:04
Again, it always goes with one mole because one mole of that substance is that many grams by the definition of molar mass.
02:11
When we do all this math, we end up with 50.
02:13
50 .7 grams of cs2.
02:17
So that is its theoretical yield.
02:20
So now to calculate percent yield, we're going to take 36 divided by 50 .7...