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Thread: basic enthalpy question

  1. #1 basic enthalpy question 
    New Member
    Join Date
    Oct 2009
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    4
    Hi

    have a basic enthalpy problem to solve.

    the reaction C2H5OH (L) + 3 O2 (g) to 2 O2(g) + 3 H20 (L) at CONSTANT VOLUME
    AT 298K relaeases 1368 kj per mol

    Using the simplification of ideal gas behvaviour (pv = nrt), what is th enthalpy of the reaction?

    I get this far, (using D for delta or the triangle)

    H = U + PV
    DH = DU + DPV
    DH = DU + Dnrt <---- then assume a constant temperature of 298
    DH = DU + Dn * RT
    DH = DU -1 * 2480

    Then i don't know what to do. I think that the heat change at constant volume is the same as the internal energy change but that isn't mentioned in the book i am working through so I don't know how it would expect me to apply it in the solution.

    If i'm correct

    DH = -1368000 - 2480
    DH = - 1370 kj per mol

    However i don't know if i have mixed up my du and dh

    Many thanks


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