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Homework Help: Need Help Understanding Heat of Rxn and Q

  1. Dec 13, 2017 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    q = mCat

    3. The attempt at a solution
    I'm kinda confused the different between Hrxn and q? I know the reaction warms the water with q=mcat = 150*4.18*(59.5-20)=24766.5 J. This is the heat released from 1.25 grams of Ca which is 0.03 moles of Ca. But, the reaction equation only have calcium per 1 mole so i thought that i would divide q by 0.03 = 825550 J or 825KJ, but this is not an answer.

    Can someone help me with these heat problems? Thanks
  2. jcsd
  3. Dec 13, 2017 #2
    Nevermind everyone. It seems like i didn't enter enough decimals here. So, my answer is 794052
  4. Dec 14, 2017 #3


    User Avatar

    Staff: Mentor

    Exactly. Don't round down intermediate results during calculations (that is, report them rounded down, but calculate with a full accuracy, or at least several "guard digits").
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