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Page 1

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Oxidation States and Half Equations

(Done on the computer to help understand the changes better!)

The element which changes it's OXIDATION STATE is the one which is either losing or
gaining e¯`s

Example 1

I¯ I

2I¯ I + 2 e¯

Here the element only needs to lose two electrons,…

Page 2

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4H + SO²¯ + 2e¯ SO + 4HO

From the equation we can see that both sides of the equation have an overall charge of 0.

Example 3

Sometimes compounds can carry different charges to expected, and also don't require all
three of HO and H.

Here we are going…

Page 3

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Now to consider the oxidation numbers of each of the elements, be careful!

2Cr³ CrO²¯

2Cr³ CrO²¯

Page 4

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2Cr³ CrO²¯ + 6e¯

As usual we need to balance our oxygens, this time adding them to the left-hand side.

7HO + 2Cr³ CrO²¯ + 6e¯

And then balance the H on the right-hand side, remember we need 14 H

7HO + 2Cr³ CrO²¯ + 6e¯ + 14H

Make sure…


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