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Temperature and Heat - what am i doing wrong?

  1. Jun 17, 2009 #1
    1. The problem statement, all variables and given/known data

    lf = 79500 cal/kg ,
    lv = 5.4 × 105 cal/kg ,
    c = 1000 cal/kg ◦ C.

    9 kg of ice at 0◦C is converted to steam at
    100◦C.
    How much heat is needed? Answer in units
    of kcal.


    2. Relevant equations

    q=mct

    3. The attempt at a solution

    100*9kg + 79.5 + 540 = 1519.5

    I am getting this wrong I dont know why
     
  2. jcsd
  3. Jun 17, 2009 #2

    cepheid

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    Science Advisor
    Gold Member

    Can you explain what each term in your attempted solution means? They don't seem to make sense. They don't match the numbers given in the problem? It would be helpful if you explained what you were doing.

    Also, what three processes (involving heat) have to occur in order to get from ice at 0C to steam at 100C?
     
  4. Jun 18, 2009 #3

    Redbelly98

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    Staff Emeritus
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    Homework Helper

    If lf is 79500 cal/kg, and you have 9 kg of ice, then how much energy is required to melt the ice?

    Hint: the answer it not 79.5.

    Also, what is the value of c for water?
     
  5. Jun 21, 2009 #4
    I got the answer! Thanks for your help.
     
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