Balancing Redox reactions

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Ghadir Seder 1G
Posts: 134
Joined: Sat Sep 14, 2019 12:17 am

Balancing Redox reactions

Postby Ghadir Seder 1G » Tue Mar 03, 2020 10:44 pm

How do I balance a reduction half reaction step by step? I am fairly confused :( the reaction is Cr2072----->Cr3+

Thank you!

Alicia Lin 2F
Posts: 83
Joined: Wed Sep 18, 2019 12:17 am

Re: Balancing Redox reactions

Postby Alicia Lin 2F » Tue Mar 03, 2020 11:05 pm

First balance the Cr by making the Cr on the right have a 3 as a coefficient. Then balance the oxygen by adding 7 H2O to the right. Then balance the Hydrogen by adding 14 H+ to the left. Then balance the charge by adding 6 electrons to the left. The book recommends balancing the main element first then the oxygens then the hydrogens then the charges.

Max Madrzyk Dis 4G
Posts: 102
Joined: Wed Sep 18, 2019 12:21 am

Re: Balancing Redox reactions

Postby Max Madrzyk Dis 4G » Tue Mar 03, 2020 11:34 pm

1. balance elements
2. balance oxygens (use h20)
3. balance hydrogens (use H+ for acidic and OH- for basic)
4. balance charge (with electrons)
5. multiply half reactions so the electrons cancel
6. combine half reactions

Eunice Nguyen 4I
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

Re: Balancing Redox reactions

Postby Eunice Nguyen 4I » Wed Mar 04, 2020 2:41 am

1. Separate the half reactions
2. Balance all of the elements that aren't oxygen or hydrogen
3. Add H2O to balance oxygen
4. Add protons (H+) to balance hydrogen
5. Balance charge of each equation with electrons
6. Scale the equations so that the amount of electrons are equal on both sides
7. Add the reactions and cancel out the similar terms

Posts: 94
Joined: Wed Sep 18, 2019 12:18 am

Re: Balancing Redox reactions

Postby JohannaPerezH2F » Wed Mar 04, 2020 9:29 am

- Balance elements in the equation other than O and H.
- Balance the oxygen atoms by adding the appropriate number of water (H2O) molecules to the opposite side of the equation.
- Balance the hydrogen atoms (including those added in step 2 to balance the oxygen atom) by adding H+ ions to the opposite side of the equation.
- Add up the charges on each side. Make them equal by adding enough electrons (e-) to the more positive side. (Rule of thumb: e- and H+ are almost always on the same side.)
- The e- on each side must be made equal; if they are not equal, they must be multiplied by appropriate integers (the lowest common multiple) to be made the same.
- The half-equations are added together, canceling out the electrons to form one balanced equation. Common terms should also be canceled out.
- (If the equation is being balanced in a basic solution, through the addition of one more step, the appropriate number of OH- must be added to turn the remaining H+ into water molecules.)
- The equation can now be checked to make sure that it is balanced.

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