Writing and Balancing Half Reactions

[Natalie LeRaybaud 1G]

Does anyone have a simple step by step method to forming and balancing half reactions because I always seem to get lost along the way.

[Harrison Wang 1H]

1. Identify the key element that undergoes an oxidation state change.
2. Balance the number of atoms of the key element on both sides.
3. Add the appropriate number of electrons to compensate for the change of oxidation state.
4. Add H+ (in acid medium), or OH- (in basic medium), to balance the charge on both sides of the half-reactions; and H2O, if necessary, to balance the equations.

[Abby Ellstrom 1I]

1. Identify which species is being oxidized and which is being reduced.
2. Separate into half reactions.
3. For each one, balance the oxygen by adding H2O to the other side for each O you need.
4. Then balance the hydrogen by adding H+ to the side that needs it.
5. Make sure the reduction and oxidation questions are transferring the same number of electrons.
6. Combine them and cancel out species that appear on both sides of the arrow (including electrons).

[lindsay lathrop 2C]

1) Determine Oxidation Numbers
2) Figure out the changes in oxidation
3) Write out the half-reactions
4) Balance the reactions
a) Balance the atoms other than H and O
b) Add H2O to balance O, and H+ to balance H
c) Balance the charges with e-
e) Multiply half-reactions to make e- equal on both sides

*if it is in a basic solution the last step you need to do it add one OH- to both sides for every H+ , and then cancel all the extra H2Os

[lindsay lathrop 2C]

https://youtu.be/v5sDNmYCaqo

I got those steps from this video, it really helped me understand it better

[Jacob Cho 2L]

1. Identify which species is being oxidized and which is being reduced (ignore H and O, and use changes in oxidation numbers)
2. Write the half-reactions for the oxidizing and reducing reagents identified in step 1.
3. For each one, balance the oxygen by adding H2O to the other side for each O you need. Then balance the hydrogen by adding H+ to the side that needs it if in an acidic solution; in a basic solution, use OH-.
4. Make sure to balance the reduction and oxidation half-reactions so that they are transferring the same number of electrons.
5. Combine them and cancel out species that appear on both sides of the arrow (including electrons).

[Erik Khong 2E]

There is actually a toolbox section in the textbook that you can use to easily follow along the steps and see them in action on page 563.