1. Redox Oxidizing and Reducing Agents
AICE Chemistry
Redox
Oxidizing and Reducing Agents

2. A Quick Review Oxidation: Reduction:
A positive direction change in oxidation state.
Or … an increase in the oxidation state from reactant to product.
Caused by the loss of one or more electrons.
A negative direction change in oxidation state.
Or … a decrease in the oxidation state from reactant to product.
Caused by the gain of one or more electrons.
Electrons

3. An Important Understanding:
You should think of oxidation and reduction as being “symbiotic”.
Neither can occur without the other.
That means that if there is an oxidation, there must also be a reduction.
Put another way – if something is to lose electrons (and be oxidized), there must be something else to gain those electrons (and be reduced).
something losing
something gaining
Electrons

4. Some Difficult Definitions:
Oxidizing Agent:
This is the particle or substance that causes oxidation in something else.
It does this by taking electrons from that other substance.
Reducing Agent:
This is the particle or substance that causes reduction in something else.
It does this by giving electrons to that other substance.

5. Consider this visual representation:
Loses electrons
Gains electrons
Electrons
By losing electrons, this particle is oxidized.
But, he is supplying electrons to the other substance who will be reduced because he gains those electrons.
There fore, this particle is a reducing agent.
By gaining electrons, this particle is reduced.
But, he is taking electrons from the other substance who will be oxidized because he lost those electrons.
Therefore, this particle is an oxidizing agent.

6. Let’s Look at a Previous Example
Zn S  ZnS
oxidation
reduction
Zn  Zn e-
S e-  S-2
Here is the oxidation half-reaction.
Here is the reduction half-reaction.

7. Continuing… Zn  Zn+2 + 2 e- S + 2 e-  S-2
Here is the oxidation half-reaction.
Here is the reduction half-reaction.
Connecting this with the new concepts:
The Zn has lost 2 electrons and has been oxidized.
These electrons were gained by the S , enabling it to be reduced.
That means that the Zn provided the electrons to the S , so the Zn is a
reducing agent in this reaction.
The S has taken the electrons from the Zn, enabling it to be oxidized.
That means that the S is an oxidizing agent in this reaction.

8. Two conclusions for you:
The particle that is oxidized is the reducing agent.
The particle that is reduced is the oxidizing agent.

9. Now for your tasks: For each of the reactions on the following slide:
Write a balanced equation for the reaction
Determine what is oxidized.
Determine what is reduced.
Write the oxidation half-reaction.
Write the reduction half-reaction.
Identify the oxidizing agent.
Identify the reducing agent.

10. Reactions: Copper + silver nitrate  copper (II) nitrate + silver
Chlorine + sodium bromide  sodium chloride + bromine
Magnesium + hydrochloric acid  magnesium chloride + hydrogen
Iron + bromine  iron (III) bromide