00:01
So let's take a look at the reaction between silicon dioxide and carbon.
00:10
And so silicon dioxide is sio2.
00:16
When we take a look at carbon, carbon is just c.
00:19
And when that reaction progresses, we're going to create silicon and carbon monoxide.
00:27
Now after we write out each of our substances, we need to make sure we balance the equation.
00:32
We have two oxygens on the left, only one on the right.
00:36
So we have to put a two in front of the co.
00:39
That puts the carbon out of balance.
00:41
There's two carbons on the right now.
00:43
So we have to put two carbons on the left to balance this out.
00:47
So this is our balanced chemical equation.
00:50
Now what we know is that we have 155 .8 kilograms of silicon dioxide.
01:03
Side and we have 78 .3 kilograms of carbon and that we wind up producing 66 .1 kilograms of silicon.
01:19
And we want to see how good we did in this particular reaction.
01:22
Is 66 .1 kilograms good or not good? so in order to take a look at this, we have to figure out the limiting reactant.
01:30
We're going to have to figure out how much we should have made in terms of silicon and then compare it to our 66 .1 kilograms to figure out our percent yield.
01:39
So the first thing we're going to do is figure out our limiting reactant.
01:43
And to figure out limiting reactant, we need to take each of our reactant amounts, our masses, and convert them into moles of silicon.
01:53
And the one that gives us the lower moles of silicon will be our limiting reactant.
01:58
Now when we do this, we need molar mass.
02:01
We're going to have to do some stoichiometry.
02:03
Molar masses in grams per mole.
02:05
So we're going to have to use grams instead of kilograms.
02:09
So when we start out with our sio2, our 155 .8 kilograms of sio2, we're first going to have to convert that into kilograms.
02:25
And every kilogram is the same.
02:27
Oops, let me turn that around.
02:30
We should have the fact that every 1 ,000 grams is a kilogram.
02:38
So now we would be in grams because the kilograms would cancel out.
02:43
And we can now convert grams into moles and we do that with molar mass.
02:48
So we have to find the mass of silicon and two oxygens and put them together.
02:53
And one mole of sio2 has a molar mass of 60 .08 grams.
03:02
So that gets us to moles, but now we need to convert to silicon.
03:06
And so the mole ratio, we have a mole of silicon for every one mole of silicon dioxide.
03:20
And so our grams cancel, these moles cancel, and we're left with moles of silicon.
03:27
That's going to give us to four significant figures, 2 ,593 moles of silicon...