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Heat problem

  1. Dec 3, 2009 #1
    1. The problem statement, all variables and given/known data
    How much heat in kcal is required to change 1.0 kg of ice, originally at -30 degrees C, into steam at 120 degrees C? Assume 1.0 atm of pressure. (Please use the following values for the constants needed in the problem: Latent heat of fusion=79.7 kcal/kg; Specific heat of ice=0.5 kcal/kg/K; Latent heat of vaporization=539 kcal/kg; Specific heat of water 1.0 kcal/kg/K; Specific heat of steam=0.480 kcal/kg)


    2. Relevant equations
    Qmelt=mLfusion
    Qfreeze=-mLfusion
    Qvaporization=mLvaporization
    Qcondensation=-mLvaporization


    3. The attempt at a solution
    Quite honestly, I don't even know how to start. I don't see how the 1.0 atm of pressure is involved in the equations.

    Could somebody just tell me how to start this off and I'll take it from there.

    I've been reading from my book but it's not clear.

    I had originally tried to use the equation Q=cmT, with the values plugged in as Q=4186*1*150, giving me 627.9 kilocalories, but this is incorrect.
     
  2. jcsd
  3. Dec 3, 2009 #2

    rl.bhat

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    Homework Helper

    Divide the problen into five sections.
    i) Q1 = m*ci*ΔT----(1)
    ii) Q2 = m*Lfreeze -----(2)
    similarly right the remaining equations and find the total Q..
     
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