Balanced Redox Reactions

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Vanessa Romero-Campos 2B
Posts: 39
Joined: Fri Sep 25, 2015 3:00 am

Balanced Redox Reactions

Postby Vanessa Romero-Campos 2B » Mon Feb 19, 2018 6:41 pm

When balancing redox reactions and we have to add water to the reaction does it matter where water is added (product or reactants side)?
I was reading the text posted on the class website and it says: "Because there are four oxygen atoms in MnO4- that are not present in the final Mn2+ form, we must add water to the product side. We add four waters to the side opposite of the four oxygen atoms to balance the oxygens:MnO4- +8H+ +5e- →Mn2+ +4H2O"

What if we have Mn2+ + 4H2O --->MnO4- +8H+ +5e- do we have to flip the reaction so that water is on the product side?

Wayland Leung
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Joined: Sat Jul 22, 2017 3:00 am
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Re: Balanced Redox Reactions

Postby Wayland Leung » Mon Feb 19, 2018 6:58 pm

The water is added to balance out the H+ or H3O+ ions in the reaction. It doesn't matter which side you add water. Water is added to balance out the hydrogens in the reaction. Water is there only for an acidic solution and an aqueous solution.

Angela 1K
Posts: 80
Joined: Fri Sep 29, 2017 7:05 am

Re: Balanced Redox Reactions

Postby Angela 1K » Mon Feb 19, 2018 9:34 pm

To expand on that answer:

You only add H2O when you need to balance out the oxygens in an equation. In the end (your answer), it doesn't matter which side the water molecules are on. We can add these water molecules because we assume that all these reactions occur in aqueous solutions, and so water is always present.

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