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Homework Help: Specific and Latent Heat

  1. Mar 25, 2010 #1
    1. The problem statement, all variables and given/known data
    Calculate the energy need to change 9 g of ice at -20 degrees Celsius to steam at 110 degrees Celsius. (C for ice=2.06 J/g, C for water=4.18 J/g, C for steam=2.02 J/g, Hf of ice=334 J/g, Hv of water=2260 J/g)

    2. Relevant equations
    Q=hv / Q=mHf / Q=mc(delta)t

    3. The attempt at a solution
    Q=(9 X 2.06 X 20) + (9 X 334) + (9 X 2.06 X 110) + (9 X 2260) + (9 X 2.06 X 110) = 27795 J

    Okay so I did this problem in class with a group, but looking back on it, I think it is wrong. But I'm not sure! I'm just very very very confused on what to do. Step by step instructions would help!! And the answer has to be in joules not calories. Thanks!! :)
  2. jcsd
  3. Mar 25, 2010 #2


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    Hi SimplySydney, welcome to PF. What are the processes that the material (originally a solid at -20C) has to go through to reach the vapor form at 110C? It looks like the first two terms represent the energy needed to heat ice to 0C and the energy needed to melt it to form liquid at 0C. What do the other terms represent?
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