Balancing Redox Reaction by Half Reaction Method

In summary, the conversation discusses the half-reaction method for balancing equations involving compounds. The individual steps for balancing the oxidation and reduction reactions are explained, with clarification on the role of spectator ions. It is determined that Cl- is a spectator ion in the given equation, and thus does not need to be balanced as it does not change during the reaction.
  • #1
moouers
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0

Homework Statement


CuCl2(aq)+Al(s)→AlCl3(aq)+Cu(s)


Homework Equations





The Attempt at a Solution



I'm just not sure what to do with a situation involving compounds. I can do simple balancing without a problem. Here is my attempt. Please, please let me know where I went wrong...

Oxidation: Al→Al+3+3e-
Reduction: Cu+2+2e-→Cu
Reduction: 2Cl-2→3Cl-3 (?)

I'm confuzzled. I don't know where to go from here, or even if I did the above correctly. The book is pretty awful in describing these half-reaction equations, so I've been searching online but without any applicable results. I didn't think I should split the reduction into two parts, but maybe I do. I don't know. I also don't know what to do with the equation concerning the Chlorine. All around, I'm confused.

I can balance the equation just fine with the "trial and error" method, and it matches the back of the book, I just don't know how to get there by half-reactions.

Thank you so much for any help.
 
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  • #2
Cl- is just a spectator and doesn't change during the reaction. Yes, you should split.

Check ChemBuddy page on the half reaction method. If it doesn't help, ask for clarification (here or there).
 
  • #3
Well, gee. That was simple! Thank you very much, and thank you for the link. I suppose what got me then was my assumption that I understood spectator ions pretty well. I guess not! In this case, is Cl- a spectator because we don't need to balance the charge since it stays the same throughout the reaction?
 
  • #4
moouers said:
In this case, is Cl- a spectator because we don't need to balance the charge since it stays the same throughout the reaction?

It is a spectator because it doesn't take part in the reaction. It doesn't take part in the reaction - so it doesn't change its charge.
 
  • #5
Got it. Thanks.
 

1. How do I identify which atoms are undergoing oxidation and reduction in a redox reaction?

In a redox reaction, oxidation is defined as the loss of electrons, while reduction is defined as the gain of electrons. You can identify which atoms are undergoing oxidation or reduction by looking at their oxidation states. An increase in oxidation state indicates oxidation, while a decrease indicates reduction.

2. What is the purpose of balancing a redox reaction by the half reaction method?

The half reaction method is used to balance a redox reaction by breaking it down into two separate half reactions, one for the oxidation process and one for the reduction process. This method allows for the conservation of mass and charge in the overall reaction.

3. How do I know which species are present in acidic or basic solutions when balancing redox reactions?

In acidic solutions, protons (H+) are present, so you will need to add H+ ions to balance the charges on the reactants and products. In basic solutions, hydroxide ions (OH-) are present, so you will need to add OH- ions to balance the charges.

4. Can I balance a redox reaction by simply adding coefficients in front of the species?

No, balancing a redox reaction requires not only adding coefficients, but also balancing the number of atoms and charges on both sides of the reaction. This is why the half reaction method is often used, as it allows for a systematic approach to balancing redox reactions.

5. Is it necessary to include spectator ions when balancing a redox reaction by the half reaction method?

No, spectator ions, which are present in the reaction but do not undergo any changes, can be omitted when using the half reaction method. This method only focuses on the species that are undergoing oxidation or reduction.

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