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Homework Help: Using Hess' Law calculate the molar enthalpy of reaction for the combustion of ethene

  1. Oct 23, 2011 #1
    1. The problem statement, all variables and given/known data
    Using Hess's Law and any necessary information from your Data Booklet, calculate the molar enthalpy of reaction for the combustion of ethene in kJ/mol.

    im so lost!
    i was gonna find each sections molar en thalpy and then balance it but whats oxygens and do i multiply it by 3?


    3. The attempt at a solution
    C2H4 + 3 O2 --------------- 2CO2 + 2H2O

    (+52.4)----->[2 x -393.5) + (2 x -285.8)] -[ 3 x 0)]


    shouldnt there be three formulas basically?
    so:
    formation of 3O2 ------->
    formation of 2H2O------>
    formation of 2CO2------->

    and then their enthalpy change?

    then i balance all three and get the answer to


    C2H4 + 3O2 ---> 2CO2 + 2H2O
    ?

    can someone help with the three fomulas please?
    thankyou!
     
  2. jcsd
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