Vandenbout Worksheet 9 Key

Vandenbout Worksheet 9 Key - When this occurs, we need to...

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KEY Review: Worksheet on Balancing Redox Equations Two methods are often mentioned for balancing redox reactions: the half reaction method and the change in oxidation method. They actually involve the same procedure. In the first case you separate out the oxidation and reduction half reaction and in the second case, you do it all at once. I prefer the latter. The half reaction method is shown in the text but I will explain the change in oxidation method here. Change in Oxidation Procedure: a. Write out as much of the unbalanced reaction as possible b. Assign oxidation numbers c. Draw brackets to connect the atoms that are oxidized and the atoms that are reduced. Write the net increases and decreases in electrons. d. Find the factors that create the least common multiple and use these to assign balanced stoichiometry for the reaction.
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Complication: pH-dependent redox reactions. Very often we will work with redox reactions that are dependent on the acidity or basicity of a reaction.
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Unformatted text preview: When this occurs, we need to balance the numbers of O and H atoms that appear in H + , OH-and H 2 O species in the reaction. For example, in acid MnO 4- Mn 2+ is a 5 electron process in base MnO 4- MnO 2 is a 3 electron process Note the change in oxidation number means a different equivalent weight for the MnO 4-depending on the reaction. So we need to add an additional step in balancing redox reactions: e/f. Rules for acid solution: balance O by adding H 2 O, then balance H by adding H + Rules for basic solution: for each O, add two OH-to side needing O and one H 2 O to other side for each H + , add one H 2 O to side needing H + and one OH-to other side. [Alternatively for base simply first balance in acid, then add enough OH-to neutralize all the H + followed by cancelling out any H 2 O that appears on each side of the reaction.]...
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This note was uploaded on 04/08/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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Vandenbout Worksheet 9 Key - When this occurs, we need to...

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