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Homework Help: Q=cmT why is this not working?

  1. May 17, 2010 #1
    1. The problem statement, all variables and given/known data

    How much heat (in kcal) must be removed to make ice at –10°C from 2 kg of water at 20°C? (The specific heat of ice is 0.5 cal/g °C.)

    2. Relevant equations

    Q=cmT

    3. The attempt at a solution

    I thought this problem was simple,
    Q=0.5x2000x30
    Then diving by 1000 again to put it into Kcal. 30 is not the right answer.
     
  2. jcsd
  3. May 17, 2010 #2

    Mark44

    Staff: Mentor

    And the specific heat of water is 1.0 cal/g °C.
    There are three things you have to account for:
    The water has to be cooled 20°C.
    The water at 0°C has to be converted to ice. (80C/g)
    The ice at 0°C has to be cooled to -10°C.
     
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