MCAT Physical : Half Reactions and Balancing Equations

Study concepts, example questions & explanations for MCAT Physical

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Example Questions

Example Question #1 : Half Reactions And Balancing Equations

Consider the redox reaction:

What is the balanced equation for the above redox reaction in acidic solution?

Possible Answers:

Correct answer:


1. Determine the oxidation number of each element.



2. Write and balance the half reactions.

Oxidation (loss of electrons):

Reduction (gain of electrons): 

3. Balance oxygen by adding water (from the solution) into the half reactions.



4. Balance hydrogen by adding  ions from the acid into the half reactions.



5. Multiply each half reaction times an integer such that the electrons cancel when the equations are added. The oxidation reaction will be multiplied by five, and the reduction reaction will be multiplied by two.

Oxidation times 5: 

Reduction times 2: 

6. Add the half reactions together. The electrons will cancel from both the reactants and products.



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