How to balance equations using the half cell method?

In summary, the given equation involves a redox reaction between SO32-, MnO4-, H+, and SO42- to form Mn2+, SO42-, and H2O. The process for balancing the equation involves dividing it into half-reactions, balancing atoms other than H and O, adding H2O and H+ to balance oxygen and hydrogen atoms, respectively, balancing the charge by adding electrons, and finally adding the two half-reactions together. This may be more challenging than other redox problems as it is not immediately clear which species is being reduced or oxidized based on the superscripts alone.
  • #1
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SO32- +MnO4-1+H+1 <-> Mn2+ +SO42- +H20(l)
 
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  • #2
Step 1 Divide the skeleton equation into half-reactions.

Step 2 Balance atoms other than H and O.

Step 3 Balance oxygen atoms by adding H2O to the side that needs O.

Step 4 Balance hydrogen by adding H+ to the side that needs H.

Step 5 Balance the charge by adding electrons.

Step 6 Make the electrons gained equal to the electrons lost and then add the two half-reactions.

Step 7 Cancel anything that is the same on both sides.
 
  • #4
this problem may seem a bit more tricky than the redox problems that you are used to since it may not be obvious which is getting reduced/oxidized based upon the superscripts alone.

The half-reactions are:

[tex]SO_3^{2-} + H_2O \rightarrow SO_4^{2-} + 2H^+ + 2e^-[/tex]
[tex]MnO_4^{-1} + 8H^+ + 5e^- \rightarrow Mn^{+2} + 4H_2O[/tex]

Make your electrons equal by multiplying the half rxns to make the number of electrons 10 for both, then add the half rxns up and you should get the correct answer.
 

Related to How to balance equations using the half cell method?

1. What is the half cell method for balancing equations?

The half cell method is a technique used to balance redox equations, where one half of the reaction is balanced at a time by separating it into two half reactions and balancing the number of electrons transferred in each half reaction. This method is especially useful for balancing more complex redox reactions.

2. How do I determine the half reactions in a redox equation?

To determine the half reactions, you must first identify the species that are being oxidized and reduced. The oxidizing agent is the species that causes the other species to lose electrons (oxidation) and the reducing agent is the species that causes the other species to gain electrons (reduction).

3. What are the steps for balancing equations using the half cell method?

The steps for balancing equations using the half cell method are:

1. Write the unbalanced equation and identify the species being oxidized and reduced.

2. Split the equation into two half reactions, one for oxidation and one for reduction.

3. Balance the atoms (other than oxygen and hydrogen) in each half reaction by adding coefficients as needed.

4. Balance the oxygen atoms by adding water molecules (H2O) to the side that needs it.

5. Balance the hydrogen atoms by adding hydrogen ions (H+) to the side that needs it.

6. Balance the charges by adding electrons (e-) to the side that needs it.

7. Multiply the half reactions by appropriate coefficients to ensure that the number of electrons transferred is the same in both half reactions.

8. Add the two half reactions together and cancel out any common species on both sides of the equation.

4. What are some tips for balancing equations using the half cell method?

Some tips for balancing equations using the half cell method include:

- Start by balancing the atoms (other than oxygen and hydrogen) in each half reaction.

- Balance oxygen atoms by adding water molecules (H2O) and hydrogen atoms by adding hydrogen ions (H+).

- Balance charges by adding electrons (e-).

- Multiply the half reactions by appropriate coefficients to ensure that the number of electrons transferred is the same in both half reactions.

- Check your final balanced equation to make sure that the number of atoms and charges are the same on both sides.

5. How is the half cell method different from the oxidation number method?

The half cell method involves separating the redox equation into two half reactions and balancing the number of electrons transferred in each half reaction, while the oxidation number method involves assigning oxidation numbers to each element in the reaction and using the changes in oxidation numbers to balance the equation. The half cell method is generally more useful for balancing complex redox reactions, while the oxidation number method is more straightforward for simple reactions.

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