Balancing Redox Reaction Video Lessons

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Problem: Balance the reaction of dichromate at the cathode and I- at the anode in acid. What is the sum of the coefficients of the balanced reaction?1) 322) 333) 124) 24

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We are being asked to balance the reaction of dichromate at the cathode and I- at the anode in acid

Recall: 

lose electrons  oxidation → anode
gain electrons  reduction → cathode


Cathode:   Cr2O72-(aq) Cr3+(aq)
Anode:       I-(aq) I2(aq)


When balancing redox reactions under acidic conditions, we will follow the following steps.

Step 1: Separate the whole reaction into half-reactions
Step 2: Balance the non-hydrogen and non-oxygen elements first
Step 3: Balance oxygen by adding H2O to the side that needs oxygen (1 O: 1 H2O)
Step 4: Balance hydrogen by adding H+ to the side that needs hydrogen (1 H: 1 H+)
Step 5: Balance the charges: add electrons to the more positive side (or less negative side)
Step 6: Balance electrons on the two half-reactions
Step 7: Get the overall reaction by adding the two reaction

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Problem Details

Balance the reaction of dichromate at the cathode and I- at the anode in acid. What is the sum of the coefficients of the balanced reaction?

1) 32

2) 33

3) 12

4) 24

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