00:02
Hi there.
00:02
In this question, we have four equations that we need to balance and classify the type of reaction.
00:09
So let's go ahead and get started here, our first one.
00:14
And i am going to omit the states of matter as i write these because the states of matter are not important for balancing.
00:22
What is important is the number of atoms on each side.
00:25
We need to make the number of atoms on each side of the equation the same.
00:30
So that our balanced equations satisfy the law of conservation of mass, meaning that we're not creating or destroying mass.
00:40
Okay, so our first reaction here, we see that we have a hydrocarbon reacting with oxygen to produce carbon dioxide and water.
00:50
So this has the general form of c to the x, h to the y reacting with oxygen, to always produce these same two products, making this a combustion reaction.
01:02
So this would be combustion.
01:04
And now let's go ahead and balance it.
01:06
There are three carbon on the left, so we need a three in front of co2 to give us three carbons on the right.
01:12
There are eight hydrogen on the left, so we need a four in front of h2o to give us eight hydrogen.
01:18
Now let's add up our oxygen.
01:20
We have three times two or six oxygen in co2 and four more in the water for a total of 10.
01:28
That means we need a 5 in front of the 02 on the left to balance this equation.
01:36
All right.
01:37
So this is our balanced combustion reaction.
01:44
For our next reaction, we see that we have potassium, and it's reacting with water.
01:52
But for the sake of identifying the type of reaction, i'm going to write water as hoh.
01:58
Then we see that we're producing k -o -h, which is now aquaous, and how much.
02:04
Hydrogen.
02:08
All right.
02:08
So what we see happens is the k comes and replaces the hydrogen.
02:15
That's how we get k -o -h and hydrogen by itself.
02:18
Therefore, this is a single replacement because there's one element being replaced.
02:26
Okay, let's go ahead and balance this now.
02:31
And in fact, let me go ahead and write water as h -2 -0 as we do this.
02:38
Okay.
02:40
So an actually, if we look, we have one potassium on each side, one oxygen on each side.
02:46
But on the right side, we have three hydrogen.
02:49
And on the left, we have h2.
02:51
So there's no way we can make, we can add a coefficient in front of h2, a whole number coefficient, and get an odd number.
02:58
So i know i need an even number of hydrogen on the right.
03:02
So i'm going to put a two in front of k -o -h.
03:05
That gives me an even number of hydrogen.
03:07
Two plus two more is four...
