Chemistry Forum

Posted: **Sun Oct 25, 2015 2:54 pm**

How do I balance these equations? Please explain the half equations as well.

Fe²⁺ + MnO₄^- ----> Fe³⁺ + MnO₂

H₂O₂ + Cr³⁺ ----> CrO₄^2- + OH^-

Posted: **Tue Aug 23, 2016 9:42 pm**

Split into half reactions, removing spectator ions and water and its ions.

Balance Oxygen using water. Balance Hydrogen using protons. Then balance the charges using electrons. Merge so that electrons cancel.

Note: To make alkaline, add sufficient

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OH&#123;-&#125;

on both sides to neutralise all

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H&#123;+&#125;

(make water) and then cancel any water common to both sides.

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 Fe&#123;2+&#125; + MnO4&#123;-&#125; = Fe&#123;3+&#125; + MnO2

Split in Half:

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 Fe&#123;2+&#125; = Fe&#123;3+&#125; || MnO4&#123;-&#125; = MnO2

Balance O:

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 Fe&#123;2+&#125; = Fe&#123;3+&#125; || MnO4&#123;-&#125; = MnO2 + 2 H2O

Balance H:

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 Fe&#123;2+&#125; = Fe&#123;3+&#125; || MnO4&#123;-&#125; + 4 H&#123;+&#125; = MnO2 + 2 H2O

Balance e:

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 3 Fe&#123;2+&#125; = 3 Fe&#123;3+&#125; + 3 e || MnO4&#123;-&#125; + 4 H&#123;+&#125; + 3 e = MnO2 + 2 H2O

Merge:

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3 Fe&#123;2+&#125; + MnO4&#123;-&#125; + 4 H&#123;+&#125; = 3 Fe&#123;3+&#125; + MnO2 + 2 H2O

Now you go:

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H2O2 + Cr&#123;3+&#125; = CrO4&#123;2-&#125; + OH&#123;-&#125;

Split in Half:

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H2O2 = ? || Cr&#123;+&#125; = CrO4&#123;3-&#125;

Balance O:
Balance H:
Alkalise:
Balance e:
Merge:

Chemistry Forum

please help with redox balancing

please help with redox balancing

Re: please help with redox balancing