Writing and Balancing Half Reactions

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Natalie LeRaybaud 1G
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

Writing and Balancing Half Reactions

Postby Natalie LeRaybaud 1G » Thu Feb 22, 2018 10:51 am

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
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

Re: Writing and Balancing Half Reactions

Postby Harrison Wang 1H » Thu Feb 22, 2018 11:16 am

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
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

Re: Writing and Balancing Half Reactions

Postby Abby Ellstrom 1I » Thu Feb 22, 2018 2:37 pm

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
Posts: 29
Joined: Sat Jul 22, 2017 3:00 am

Re: Writing and Balancing Half Reactions

Postby lindsay lathrop 2C » Sat Feb 24, 2018 2:53 pm

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
Posts: 29
Joined: Sat Jul 22, 2017 3:00 am

Re: Writing and Balancing Half Reactions

Postby lindsay lathrop 2C » Sat Feb 24, 2018 2:55 pm

https://youtu.be/v5sDNmYCaqo

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

Jacob Cho 2L
Posts: 12
Joined: Fri Sep 29, 2017 7:05 am

Re: Writing and Balancing Half Reactions

Postby Jacob Cho 2L » Sat Feb 24, 2018 4:55 pm

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
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

Re: Writing and Balancing Half Reactions

Postby Erik Khong 2E » Sun Feb 25, 2018 6:37 pm

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.


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