00:01
So let's look at this reaction in a little bit more detail and take a little bit more time to balance it.
00:05
We've got magnesium reacting with phosphoric acid to produce magnesium phosphate and hydrogen gas.
00:12
To balance it, we'll need a three in front of magnesium, so we have three magnesiums, and a two in front of phosphoric acid.
00:21
So we have two phosphates.
00:23
This is actually supposed to be two, not three.
00:29
And then that'll give us six hydrogen, so we need a three in four.
00:32
Front of h2.
00:35
Then when we pull it apart into the ionic form, which was given, we can have it balanced.
00:41
I'm not quite sure why they didn't balance it.
00:45
To identify what was oxidized and what was reduced, oxidized doesn't need to be capitalized and reduced not, but that's a minor point.
00:57
We assign oxidation states.
01:00
Anytime we have an element by itself, its oxidation state is zero, so magnesium is zero.
01:06
Anytime we have a monotomic, ion in an ionic compound, its oxidation state is its charge.
01:14
Magnesium has a two plus charge, so that's its oxidation state.
01:19
Then we recognize hydrogen in phosphoric acid has a plus one charge, so that's its oxidation state, and hydrogen by itself in its elemental form, similar to magnesium in its elemental form, has an oxidation state of zero...