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Homework Help: Latent heat and final temperature

  1. Apr 26, 2012 #1
    1. The problem statement, all variables and given/known data

    An aluminum container whose mass is 205g contains 300g of water at 20°C. In this container is then placed 250g of iron at 150°C and 20g of ice at -10°C. Find the final temperature of the mixture.



    2. Relevant equations

    Since the heat gained by aluminum container, water, and ice is equal to heat lost by iron, then



    3. The attempt at a solution

    What is asked is the final temperature of mixture, Tmix. so,




    Lf is the latent heat of ice






    Is this correct? i think there's something wrong in my solution..
  2. jcsd
  3. Apr 26, 2012 #2
    Do this simple check to determine yourself whether your answer is correct. Take your final answer of 19.9 C and look at energy balances. You have energy lost by the vessel and its water. It is lost because the final temperature is lower than its initial temperature. Now determine how much energy the ice gained going from -10 C to 19.9 C including latent heat. Do the same for the energy loss of the iron going from 150 C to 19.9 C. Do you have a balance? If not, you did something wrong.
  4. Apr 26, 2012 #3

    i already check it. and yes it's wrong.

    is my assumption correct?
  5. Apr 26, 2012 #4
    Yes, the heat gained by the aluminum container, water, and ice equals the heat lost by iron.

    Your answer is off by about 4.5 C. I have not gone through your calculations; I only did my own.
  6. Apr 26, 2012 #5
    thank you very much sir!! i finally got the correct answer. i made a wrong computation on the right hand side of the last equation. God bless!
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