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Balancing Chemical equations

  1. Sep 14, 2013 #1
    1. The problem statement, all variables and given/known data


    "The reaction of ethane gas (C2H6) with chlorine gas produces C2H5Cl as its main product (along with HCl). In addition, the reaction invariably produces a variety of other minor products, including C2H4Cl2, C2H3Cl3, and others. Naturally, the pro- duction of these minor products reduces the yield of the main product. Calculate the percent yield of C2H5Cl if the reaction of 300. g of ethane with 650. g of chlorine produced 490. g of C2H5Cl." (Zumdahl, Chemistry, 2013)

    2. Relevant equations

    Balancing and math principles.

    3. The attempt at a solution

    Ok, I have the answer in the solution manual. It gives out 82.9%.
    But, the thing I do not understand about the way they do the problem is this:
    They use the formula C2H6+ Cl2-> C2H5Cl+ HCl
    However, that's not what is really happening. There are other products formed.
    I thought of this formula (which is missing ''the other'' products):
    C2H6+ Cl2-> C2H5Cl+ HCl +C2H4Cl2+C2H3Cl3 + others
    I found different ways of balancing this last formula if I ignore the others.

    Why does the first equation give the right answer? Won't the other molecules intervene in the calculations?
     
  2. jcsd
  3. Sep 14, 2013 #2

    chemisttree

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    Science Advisor
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    Gold Member

    No, they don't. You can't be certain the other products were produced anyway. The other "products" COULD be unreacted starting material!
     
  4. Sep 14, 2013 #3
    But, there still may be other products. I don't understand how those cannot have an impact on the reaction balancing.
     
  5. Sep 14, 2013 #4

    Borek

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    Staff: Mentor

    Theoretical yield assumes only one product.

    Note that in this particular case you can't uniquely balance reaction with several products. Each of these:

    2C2H6 + 3Cl2 -> C2H5Cl + C2H4Cl2 + 3HCl

    50C2H6 + 67Cl2 -> 33C2H5Cl + 17C2H4Cl2 + 67HCl

    1028C2H6 + 1119Cl2 -> 937C2H5Cl + 91C2H4Cl2 + 1119HCl

    is balanced OK. Which one of these is the correct one?
     
  6. Sep 14, 2013 #5
    All of them could be correct i guess. Hmm, you are intriguing me here. Theoretical yield applies only when there is one product? What about the HCl?
     
  7. Sep 14, 2013 #6

    Borek

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    Staff: Mentor

    Sorry, lousy wording, one main product. HCl doesn't matter, as its amount is related to the main product - you don't need more ethane to produce HCl.
     
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