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Converting Btu to J

  1. Apr 15, 2009 #1
    1. The problem statement, all variables and given/known data

    I am just trying to convert Btu to J based on the heat capacity of water and it is not giving me the right answer.

    2. Relevant equations



    3. The attempt at a solution

    Btu = C(water) * m(1 lb) * dt(1 F)

    1 lb = 0.454 kg
    1 F = 9/5 K

    1 Btu = 4.186 kJ/(kg*K) * .454 kg * (9/5)K = 3.42 kJ < should be 1054 J, what am I doing wrong?
     
  2. jcsd
  3. Apr 15, 2009 #2

    mgb_phys

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    Perhaps (5/9) ?
     
  4. Apr 15, 2009 #3
    I thought 1 F = 9/5*C + 32?
     
  5. Apr 15, 2009 #4

    mgb_phys

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    You want the amount of energy to heat the water through 1 fahrenheit so it's c->f
     
  6. Apr 15, 2009 #5
    I have the heat capacity of water in kJ/(kg*K) so arent I converting 1 fahrenheit degree to K?
     
  7. Apr 15, 2009 #6

    mgb_phys

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    You are calculating the energy needed to heat one pound of water through 1 f
    So just like you have the amount of kg in a lb (0.454) you also need the amount of c in an 'f' ie 5/9
     
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