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Law of quantity of heat = mass

  1. Apr 25, 2009 #1
    hi for u all

    i wanna ask a question in a thermochemistry about the law of

    quantity of heat = mass . specefic heat . change in temp

    firstly . i want to know the units of (mass ) and (heat quantity) in this law
    (gm , ml , liter)..........(joules,kj)
    Q: on adding 50 ml of diluted base on 50 ml of diluted acid in isolated cal. the temp. of the solution rises from 18.2 to 21.3 degree
    calculate the liberated heat

    thanks ...i wish u answer me quickly ....

    bye
     
  2. jcsd
  3. Apr 25, 2009 #2

    Borek

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    Staff: Mentor

    Re: thermochemistry(Q)

    ml and liter are not units of mass, but units of volume.

    Exact units used don't matter. You need to use units of mass, units of temperature and specific heat that is expressed using these units and units of energy that you want your answer to be in.
     
    Last edited: Apr 26, 2009
  4. Apr 26, 2009 #3
    Re: thermochemistry(Q)

    thank u for your answer

    but i want to know the answer of the above question
    please

    i answered it ...

    liberated heat=100 x 4.18 x (21.3-18.2)=1295.8 j =1.2958 kj
    but the answer of the book was ..1295.8 kj
    so i dont know the right answer

    thanks
     
    Last edited: Apr 26, 2009
  5. Apr 26, 2009 #4

    Borek

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    Staff: Mentor

    Re: thermochemistry(Q)

    123 cBTU.
     
  6. Apr 27, 2009 #5
    Re: thermochemistry(Q)

    i m sorry ..i didn't understand your answer ..
     
  7. Apr 27, 2009 #6

    Borek

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    Staff: Mentor

    Re: thermochemistry(Q)

    You have edited your post while I was composing mine, I have not seen your answer.

    1298 Joules or 1.298 kJ it is (assuming data you have listed is correct). 1298 kJ is wrong.
     
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