Balance Oxidation-Reduction Equations - Steps & Examples

  • Thread starter gigi9
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    Ap Chem
In summary, balancing oxidation-reduction equations involves first identifying the elements present on each side and then using coefficients to balance them. This can be demonstrated through the example of balancing the photosynthesis reaction, where carbon and hydrogen are balanced first, followed by oxygen to achieve a balanced equation. Balancing redox reactions is more complex and requires the use of half-reactions and a balancing method known as the "half-reaction method."
  • #1
gigi9
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Someone please give me a good explanation on how to "Balance Oxidation- Reduction Equations." Plz show me the steps and an example of how to do this type of equations. Thanks a lot.
 
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  • #2
gigi9,
photosynthesis might be a good example. Let's start from
H2O + CO2 -> C6H12O6 + O2.
First step, let's add what we have.
Left-hand side: 2H + 3O + 1C.
Right-hand side: 12H + 8O + 6C. So the formula is not balanced.

As a first step, we should look for an element that appears only in one component on each side. This is carbon. So, to balance carbon, we have to use 6 molecules of carbon dioxide:
H2O + 6CO2 -> C6H12O6 + O2.
Let's add what we have.
Left-hand side: 2H + 13O + 6C.
Right-hand side: 12H + 8O + 6C.

Is there another element which appears only once on each side? Yes, hydrogen! So we better use 6 molecules of water:
6H2O + 6CO2 -> C6H12O6 + O2.
Left-hand side: 12H + 18O + 6C.
Right-hand side: 12H + 8O + 6C.

We can balance this by adding more oxygen on the RHS:
6H2O + 6CO2 -> C6H12O6 + 6O2.

Now it's balanced.
 
  • #3
Originally posted by arcnets
gigi9,
photosynthesis might be a good example. Let's start from
H2O + CO2 -> C6H12O6 + O2.
First step, let's add what we have.
Left-hand side: 2H + 3O + 1C.
Right-hand side: 12H + 8O + 6C. So the formula is not balanced.

As a first step, we should look for an element that appears only in one component on each side. This is carbon. So, to balance carbon, we have to use 6 molecules of carbon dioxide:
H2O + 6CO2 -> C6H12O6 + O2.
Let's add what we have.
Left-hand side: 2H + 13O + 6C.
Right-hand side: 12H + 8O + 6C.

Is there another element which appears only once on each side? Yes, hydrogen! So we better use 6 molecules of water:
6H2O + 6CO2 -> C6H12O6 + O2.
Left-hand side: 12H + 18O + 6C.
Right-hand side: 12H + 8O + 6C.

We can balance this by adding more oxygen on the RHS:
6H2O + 6CO2 -> C6H12O6 + 6O2.

Now it's balanced.

That's good arcnets, but gigi is talking about balancing redox reactions, which is a bit more complicated than regular stoichiometry.
 
  • #4
why don't you post an example and we'll work from there gigi9.
 

1. What is oxidation-reduction (redox) reaction?

Oxidation-reduction reaction, also known as redox reaction, is a type of chemical reaction that involves the transfer of electrons between reactants. In this reaction, one reactant loses electrons (oxidation) while the other gains electrons (reduction).

2. Why is it important to balance oxidation-reduction equations?

Balancing redox equations is important because it ensures that the number of atoms and the charge are conserved on both sides of the equation. This allows us to accurately predict the products of the reaction and determine the stoichiometry of the reaction.

3. What are the steps involved in balancing a redox equation?

The steps involved in balancing a redox equation are:
1. Identify the reactants and products
2. Separate the reaction into two half-reactions, one for oxidation and one for reduction
3. Balance the atoms other than hydrogen and oxygen in each half-reaction
4. Balance the oxygen atoms by adding water molecules
5. Balance the hydrogen atoms by adding hydrogen ions
6. Balance the charges by adding electrons
7. Make the total number of electrons equal in both half-reactions by multiplying one or both of the half-reactions
8. Combine the two half-reactions and cancel out any common terms
9. Double-check to ensure that all the atoms and charges are balanced.

4. Can you provide an example of balancing a redox equation?

Yes, for example, let's balance the following redox equation:
Fe + HCl → FeCl2 + H2
1. Separate the reaction into two half-reactions:
Oxidation: Fe → Fe3+
Reduction: HCl → H+ + Cl-
2. Balance the atoms (other than hydrogen and oxygen) in each half-reaction:
Oxidation: Fe → Fe3+
Reduction: 2HCl → 2H+ + 2Cl-
3. Balance the oxygen atoms by adding water molecules:
Oxidation: Fe → Fe3+
Reduction: 2HCl → 2H+ + 2Cl- + 2H2O
4. Balance the hydrogen atoms by adding hydrogen ions:
Oxidation: Fe → Fe3+
Reduction: 2HCl + 2H+ → 2H+ + 2Cl- + 2H2O
5. Balance the charges by adding electrons:
Oxidation: Fe → Fe3+ + 3e-
Reduction: 2HCl + 2H+ + 2e- → 2H+ + 2Cl- + 2H2O
6. Make the number of electrons equal in both half-reactions by multiplying the oxidation half-reaction by 2:
2Fe → 2Fe3+ + 6e-
Reduction: 2HCl + 2H+ + 2e- → 2H+ + 2Cl- + 2H2O
7. Combine the two half-reactions and cancel out any common terms:
2Fe + 2HCl → 2FeCl2 + 2H2
8. Double-check to ensure that all the atoms and charges are balanced.
Fe + 2HCl → FeCl2 + H2

5. Are there any shortcuts or tricks for balancing redox equations?

Yes, there are a few shortcuts that can make balancing redox equations easier. Some of these tricks include:<

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