AP Chemistry - Chapter 4: Redox

AP Chemistry

Chapter 4 REDOX Reactions

Chapter 4: Redox

Redox ( Reduction and Oxidation)

Reduction means the oxidation number of an element decreases through the reaction.

Oxidation means the oxidation number of an element goes up.

Oxidation numbers are similar to charge but they are not exactly the same.

Watch the video to the right to learn how to identify them and what the difference is!

How to find oxidation numbers.mov

Identifying Oxidation Numbers

Batman is what the city needs him to be. In the clip Batman pretends to be the one who killed a bunch of people instead of Harvey Dent, a lawyer who put many criminals away. When the Joker makes Harvey go crazy and kill people the courts will be forced to set the criminals free since the prosecutor was corrupt. Batman becomes the one who did these things so that city may benefit. He says "He will be anything the city needs him to be!" Take a well deserved break and watch a couple minutes of Batman. It is inspiring!

Rules on Determining Oxidation Numbers.doc

Identifying Oxidation Numbers

Use these rules to determine the oxidation number of every element in a chemical reaction. You will have to memorize these rules but many of these rules become common sense after practicing for awhile.

Writing Half Reactions

Every REDOX reaction has an element that undergoes reduction and oxidation. You can split the reaction into both parts.

Remember Reduction means the charge goes down. Oxidation (comes from oxygen being added) means the charges goes up.

You can also say LEO says GER! Losing Electrons is Oxidation, Gaining Electrons is Reduction.

OIL RIG works too! Oxidation is losing, Reduction is Gaining!

Here is an example of each!

F + 1e- --> F- Oxidation

Cu--> Cu+1 + 1e- Reduction

Writing Half Reactions.mov

Notes on Redox Reactions and Balancing Redox Reactions.doc

Balancing Redox Equations

Practice makes perfect! Follow the rules step by step. Do not try to balance without the rules until you are extremely comfortable.

The 9 rules of balancing redox are on page 2 of the notes page!

Remember you only use this system of balancing for a REDOX reaction. (Charges are changing from reactant to product side)

You do not need to Redox everything!

Balancing Reactions Practice

Watch me balance these problems and use this as model for what ever question you are working on.

Balancing a Redox.mov

Balancing Redox Reactions.mov

Check Your Understanding:

For the two questions below, think about the question, then click on the down arrow when you have your answer to check to see if you are correct.

Use the following reaction to answer the questions below. Br-1 + MnO4- --> Br2 + Mn+2

1. What is the oxidation number of Br2?

Br2 is an element and therfore has an oxidation number of zero.

2. Which element is being reduced?

Manganese is going from a +7 to a +2, gaining 5 electrons, therefore it is being reduced.

3. What is the coefficient in front of Br2, when balanced?

5Br2 Remember to multiple your half reactions by 5 and 2 so that the electrons being given off are equal to the electrons taken in.

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