00:01
So for this problem, we have a series of chemical reactions which involves some iron.
00:05
And what we're told is that we have some potassium chlorate that then decomposes into the elements.
00:12
And when it decomposes, some of the oxygen then reacts with the iron sample to form iron oxide.
00:18
So the first thing that we need to do is we need to actually write out the chemical reactions that express this process.
00:25
So the first one, we know, is a decomposition of potassium chloride, which will decompose inside.
00:33
To its constituent elements of potassium, chlorine, as well as oxygen.
00:41
And now we just need to balance this.
00:43
Well, we look at the potassium.
00:46
Potassium is balanced.
00:48
When you look at the chlorine, the chlorine is not balanced.
00:51
We have two here on the right, but only one on the left, so we need to put a two here.
00:57
But that also unbalances the potassium, which we now need to put a two so that there's two on each side.
01:03
And then finally for the oxygen, well, we have six.
01:05
Six on the left and two on the right, so to make six on both sides, we put a three.
01:11
So that is a balanced equation for the first reaction.
01:16
Now the second reaction that we were dealing with is that the oxygen from this decomposition reaction then reacts with iron to form iron oxide.
01:24
So we know that a reaction will look like this.
01:31
Now we need to balance it.
01:34
While we first look to the oxygen, the oxygen is unbalanced.
01:41
There's two on the left and three on the right.
01:44
So to make six on both sides, i multiply this by three and i multiply this by two.
01:49
And the last thing i need to do is balance the iron.
01:51
Will i have four iron items on the right, and only one on the left, so i put a four there to balance it.
01:56
So now i have my chemical equations that represent this process.
02:01
Now i want to find the relevant molar masses for all of these compounds so that i can then do the stoichiometry with them.
02:09
So let's first to oxygen gas, which is used as a product in the first reaction and a reactant in the second one.
02:17
So i just have two oxygen atoms, which are each 16 .0, which gives the molar mass a 32 grams per mole.
02:27
Now i want to do potassium chlorate.
02:30
Well, the molar mass is just going to be one potassium, which is 39, chlorine, which is 35, and then.
02:42
And then, and then, 0 .45, and then three oxygians, which are each 16 .0.
02:47
And when i add those two together, i get 100 to 22...