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TPR G-CHEM Question

Discussion in 'MCAT Study Question Q&A' started by msw27, May 8, 2008.

  1. msw27

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    Hey guys,

    On page 455, number 9-7 of the TPR physical sciences book (2007 version), would anyone mind helping me derive where the enthalpy values that they plugged into the equation came from? Thanks:)
     
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  3. scottyT

    scottyT Real Member
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    For those without the book the question is like this:

    What is the dH for the following reaction under standard conditions?
    CH4(g) + 2O2(g) --> CO2(g) + 2H2O (l)

    I have the 2005 edition and I think it's have the same example. I think they are using standard values from some unmentioned table. I remember that I had to look this sort of stuff up when I needed it in college. I don't believe you can figure out the enthalpy of formation for the substances in the equation without outside information like a table of enthalpies or some other equations that you could balance (except for O2, that's zero b/c it's a pure substance in it's natural state). Please someone correct me if I'm wrong about this.

    It's especially confusing because they have the enthalpy of formation for CO2 as -393kJ/mol in the problem and they have it as -394kJ/mol on the preceding page. I looked up that enthalpy on wikipedia and they have it as -393.5 kJ/mol.
     
  4. msw27

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    I ended up doing the same thing, I just wanted to make sure there wasn't something I was missing. I appreciate your help:)
     

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