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Homework Help: AP Chem question

  1. Aug 31, 2003 #1
    Someone plz give me a good explaination 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.
  2. jcsd
  3. Sep 1, 2003 #2
    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.
  4. Sep 2, 2003 #3
    That's good arcnets, but gigi is talking about balancing redox reactions, which is a bit more complicated than regular stoichiometry.
  5. Sep 7, 2003 #4
    why don't you post an example and we'll work from there gigi9.
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