00:01
And this problem, we have four reactions and we're asked to balance them, the redux reactions, and balance by oxidation number method.
00:08
For my first given reaction, here's what i'm given.
00:12
And you'll notice i've written my oxidation numbers up here.
00:15
So what i did is i split this into my oxidation reduction.
00:19
Started with this initial part right here.
00:23
So on my first equation, let's go to yellow for this.
00:27
I added 12 electrons right here.
00:35
And that is based on the numbers.
00:40
Where's my sulfur? i had this one was my carbons.
00:47
My carbon, he was here was four.
00:57
My carbon was four.
00:59
My sulfur was that's six.
01:05
Six times two is 12.
01:06
Okay.
01:09
So because we had two here and four, that gives me a total of six sulfurs that are different.
01:16
Let me write those up here.
01:21
This was negative 2, and this is plus 4.
01:27
So this is 6 times 2.
01:30
And that's where you get that 12.
01:32
I have to add a co2 to accommodate my carbon right here.
01:37
And i need 12 h pluses to offset my charges, and that'll give me six waters.
01:42
For my second reaction, i needed on this one four electrons.
01:52
I needed four electrons, and we can see that my transfer here is from zero to two.
01:59
And i'm going to take that times two, so two times two times two is four, which means i need four of these, and we're all ready to go.
02:06
I have crossed out all the species that cross out, and i end up with this as my balanced chemical equation.
02:12
So there's the answer for the first one.
02:16
The second one gave me a big headache here.
02:19
I ended up balancing it.
02:21
I was having a heck of a time seeing what i was doing because i was looking at my boron and seeing three and three, but it wasn't connecting that i had a positive three on my left boron, my reactant, and a negative three on my product.
02:36
So what i did here, again, is split this up into mg and mgo, b203, and mg3b2.
02:47
I split them up into those two reactions.
02:52
Then i needed an oxygen over on this side to accommodate that oxygen.
02:59
And i needed my electrons transferred were two.
03:05
Ignore those red numbers right now, which means i needed to offset that with two hydrogens.
03:11
For my second, i only was paying attention to the borons to get started here.
03:16
And i could see that i went from a 3 plus to a 3 minus, which is where.
03:20
Where my six electrons came from.
03:23
Balance that was six, and then i need three of these over here.
03:27
Since i have six electrons, i needed to multiply this times three, which gave me three, three, six, and six...