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Homework Help: Find the ΔE of the combustion of octane in a bomb calorimeter

  1. Nov 3, 2011 #1
    1. The problem statement, all variables and given/known data

    Consider the combustion of octane that is burned in a bomb calorimter in the presence of 10.00kg of water. When burning 8.10mL of octane (.703g/ml=d) the temp. of the surrounding water increase by 5.66°C. The heat capacity of the bomb calorimter is 6.656Kj/ °C and the water is 4.184 j/g x °C
    2. Relevant equations

    qcal=Ccal x ΔT
    ΔErxn= qrxn / moles of octane

    3. The attempt at a solution

    find Q of water which gave me 236.8 KJ by q=mcΔT ( m = 10000KG )
    and find Q cal which ended up to 37.13 KJ by q=Ccal ΔT
    then I added both Heat to get 273.9 Kj and then I divided by the number of mole found which was .049852045 moles.

    However I got as an answer -5494.25 and the answer is -5506.3 Kj/mol

    P.s: why does my textbook says to just use the Q of the calorimter and not add it up to the one of water in order to find the ΔE?
  2. jcsd
  3. Nov 3, 2011 #2
    Check your arithmetic.
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