half reaction

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nshahwan 1L
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Joined: Fri Aug 30, 2019 12:18 am

half reaction

Postby nshahwan 1L » Sun Feb 23, 2020 11:43 pm

how do you know when to put water in the half reaction when balancing?

Petrina Kan 2I
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Joined: Fri Aug 30, 2019 12:17 am

Re: half reaction

Postby Petrina Kan 2I » Sun Feb 23, 2020 11:45 pm

I am confused about the same thing. In my discussion, my TA included water in the acidic redox reaction (with H2O and H3O+) but not the basic one (she only included OH- with no H2O). I am confused as to why.

andrewcj 2C
Posts: 102
Joined: Thu Jul 11, 2019 12:17 am

Re: half reaction

Postby andrewcj 2C » Sun Feb 23, 2020 11:47 pm

In acidic solution, you add water to balance out the oxygen in the half reaction.
In basic solution, you do the same as above but you also add OH- to the side with H+ in order to neutralize the acidity of that side, which makes water.

Aiden Metzner 2C
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Joined: Wed Sep 18, 2019 12:21 am

Re: half reaction

Postby Aiden Metzner 2C » Mon Feb 24, 2020 12:26 am

You include water in the half reaction when you need to balance O2 in the reaction. Then if there are left over H+ ions you include water in the reaction as well as OH- ions

CosetteBackus_4F
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Joined: Wed Feb 20, 2019 12:18 am

Re: half reaction

Postby CosetteBackus_4F » Mon Feb 24, 2020 2:38 pm

Balance oxygen with water and balance hydrogen with H+ in acidic solutions.

Abhi Vempati 2H
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

Re: half reaction

Postby Abhi Vempati 2H » Mon Feb 24, 2020 2:42 pm

Pages 538-543 in the textbook were really helpful for me, and it explains each step clearly and gives examples to follow along with. Hope this helps!

charleejohnson1L
Posts: 99
Joined: Fri Aug 30, 2019 12:17 am

Re: half reaction

Postby charleejohnson1L » Mon Feb 24, 2020 3:00 pm

it really helped me when my TA like, explicitly stated that you can only add what's already in the solution. so like if it says it's an acidic solution, the only thing in there except for the redox reaction is water and hydrogen ions, and if it says it's a basic solution, the only thing in there except for the redox reaction is water and hydroxide ions. you just keep adding either or until your redox half reactions are balanced, and then when you add your half reactions, you'll get the full reaction! I hope this helps :)

Sam McNeill 1E
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Joined: Sat Aug 24, 2019 12:17 am

Re: half reaction

Postby Sam McNeill 1E » Mon Feb 24, 2020 5:06 pm

For balancing half reactions in acidic conditions, use 1) Balance everything other than H and O 2)Balance O using H2O 3)Balance H using H+ 4)Balance charges by adding electrons 5)Add the half reactions together. For basic conditions, follow the same steps but at the end cancel out H+ by adding OH- to both sides and turning the H+ and OH- into water.

ABombino_2J
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Joined: Thu Jul 11, 2019 12:15 am

Re: half reaction

Postby ABombino_2J » Tue Feb 25, 2020 2:43 pm

Use H2O to balance the Oxygen in the reaction and then use H+ to balance the Hydrogen as a result of adding H2O. Then balance the charges by adding e-. Multiply the half reactions so that the charges cancel each other out then add the reactions together. If it is a basic solution add OH- to both sides to make water from the reaction H++OH-=H20

nshahwan 1L
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Joined: Fri Aug 30, 2019 12:18 am

Re: half reaction

Postby nshahwan 1L » Sun Mar 01, 2020 10:13 pm

thank you so much for all the great explanations!!

J_CHEN 4I
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Joined: Tue Nov 14, 2017 3:01 am

Re: half reaction

Postby J_CHEN 4I » Sun Mar 01, 2020 10:19 pm

In acidic solutions, balance the half equation with H+ and H20. For basic solutions, balance the half reaction with OH- and H20. For some cases, like the reaction (H+) + (OH-) -> H20, you might need to look for the reduction/oxidation potentials given in the book.


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