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Balancing Chemical equations

  • Thread starter alingy1
  • Start date
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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?
 

chemisttree

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No, they don't. You can't be certain the other products were produced anyway. The other "products" COULD be unreacted starting material!
 
325
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But, there still may be other products. I don't understand how those cannot have an impact on the reaction balancing.
 

Borek

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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?
 
325
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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?
 

Borek

Mentor
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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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