00:01
To balance the reaction in acidic solution, we'll use the half reaction technique, where we've got as one half reaction, selenium going to the selenate ion.
00:16
The seleniums are balanced one and one.
00:19
To balance the oxygens, we add water.
00:21
So with three oxygens on the right hand side, we'll need to add three waters to the left hand side.
00:27
That then introduces six hydrogens.
00:32
In acidic solution, we'll balance the hydrogens by adding hydrogen ions.
00:37
Then we balance the charges with electrons.
00:40
We have no charge on the left hand side and we have a four plus charge on the right hand side.
00:46
So we need to add four electrons to get a neutral charge on each side.
00:53
Then for the second half reaction, we have chromium hydroxide going to chromium metal.
01:02
We have one chromium and one chromium.
01:05
We have three oxygens, so we're going to need three waters on the right hand side.
01:12
That introduces six hydrogens.
01:16
Here we already have three hydrogens, so we just add three more hydrogens.
01:23
Now to make sure it's neutral, we've got no charge here and to make this one neutral, we need to add three electrons so that both sides have the same charge.
01:38
Then we need to sum these together so that the electrons cancel, requiring us to multiply this one by four and this one by three so that we get 12 electrons that end up canceling.
01:51
Then we have three times three, which gives us nine waters, and four times three, which gives us 12 waters.
02:01
So that's a net three waters for the right hand side.
02:06
And then we have three se and we also have 14, i'm sorry, 12 h plus and looks like 18 h plus.
02:24
So that's going to give us a net, yeah, 18 minus 12 and that's six hydrogens for the right hand side.
02:39
And then we still have four croh3 and then on the right hand side we'll also have three seo2 minus, sorry, seo3 2 minus and four chromiums.
03:10
So to verify it's balanced, we've got three seleniums on the left hand side and three on the right hand side, four chromiums and four chromiums.
03:25
We've got four times three, that's 12 oxygens.
03:29
We've got three and nine, that's 12 oxygens.
03:33
We've got four times three, that's 12 hydrogens.
03:37
We have six and six, that's 12 hydrogens.
03:40
We have no charge on this side.
03:42
We have a six plus and a six minus, so we have no charge on the right hand side...