00:01
So now we're going to work on problem 71 from chapter 8.
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In this problem, we're given several reactions, and we're asked to determine which are redox reactions.
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And for the ones that are, we need to determine what's the oxidizing agent and what is the reducing agent.
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So the first reaction, which we're given, is lithium solid reacting with oxygen gas to form a lithium.
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Oxide.
00:47
So the question now is we need to go ahead and check the oxidation states for each atom.
00:56
So for lithium, on the left side, both are in their elemental state, no charge, so both have a zero charge here.
01:06
And then on the right side, lithium has a positive one charge and oxygen has a negative two charge.
01:12
So we see that the elements are changing their oxidation numbers.
01:16
So this is a redox reaction.
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And so the question is what's the reducing agent? what's the oxidizing agent? so the reducing agent is one that is giving electrons.
01:31
That means it's losing electrons itself.
01:34
So lithium is going from zero to positive.
01:37
So it's losing electrons.
01:39
So that means it's being reduced.
01:41
It's the reducing agent.
01:42
And oxygen is gaining, which means it's being reduced.
01:47
So that means it's the agent of oxidation or the oxidizing agent.
01:56
In part b, we're given magnesium solid plus iron 2 plus aquas, and this is producing magnesium 2 plus and iron solid.
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So here it's pretty easy to see the change in charge or oxidation state.
02:24
So magnesium here is zero.
02:26
Iron is plus two.
02:29
Magnesium goes to plus two and iron goes to zero.
02:33
So this is a redox reaction.
02:38
And magnesium here is losing electrons.
02:41
That means it's the reducing agent.
02:43
It's reducing the iron...