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Homework Help: Phase Change

  1. Feb 11, 2009 #1
    Hoping someone could double-check for me....

    1. The problem statement, all variables and given/known data

    1) A 90 g block of unknown metal is heated to 86 degrees C and put in an insulated cup with 175 g water at 23 degrees C. At equilibrium, they are both 25.8 degrees C. What is the specific heat of the metal block?

    2) A well insulated cup contains 145 g of ice at 0 degrees C. We pour in 45 g watwer at 75 degrees C.
    a- Once equilibrium is established, how many grams of ice remain?
    b- What is the final temp in the cup?




    3. The attempt at a solution
    1) c ( 90 g) (-60.2 degrees c) + 1 cal/g degrees C) (175 g) (2.8degrees C) = 0
    c = 0.0904 cal/g degree C

    2)
    a- energy available to melt ice: 1 cal/ g Celcius (45 g) ( 75 degrees ) = 3375 cal
    energy needed to melt ice: 145 g (80 cal/g) = 11600 cal
    not all will melt

    80 cal /g (mass melted) = 3375 cal
    mass melted = 42.19 g

    b- Temp is 0 since there is still ice.
     
  2. jcsd
  3. Feb 11, 2009 #2

    Delphi51

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    Homework Helper

    Looks good to me!
     
  4. Feb 12, 2009 #3
    OK, great. Thanks for looking it over!
     
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