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Temp equilibrium / latent heat

  1. Dec 1, 2006 #1
    1. The problem statement, all variables and given/known data
    1 625g iron block is heared to 352 C is placed in an insulate container (of negligible heat capacity) containing 40g of water at 15 C. what is the equilibrium temp of this system? if your answer is 100 C, determine the amount of water that has vaporized.

    2. Relevant equations
    Q(block)=mc(T-Tblock) = .625(560)(T-352)

    3. The attempt at a solution
    set Q(block)=Q(water) i got T=242.95.. how was i suppose to get 100 C?

    how do i solve how many grams of water have evaporated.

    im so lost on this probelm, any help would be appreciated.
  2. jcsd
  3. Dec 1, 2006 #2


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    Science Advisor
    Homework Helper

    When water reaches 100 C it turns to steam (it boils). To turn 1g of water at 100 C into 1g of steam at 100 C requires heat energy. That energy is called the "latent heat of evaporation".

    You are doing OK so far. The equilibrium temp would have been 243 if the water didn't boil. but we know water boils at 100, therefore some water DID boil.

    Heat out of block as it cools to 100 = heat into water to raise all the water to 100 + latent heat to convert some of the water to steam at 100.
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