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Homework Help: Two Fairly Basic Thermodynamics Questions

  1. Feb 12, 2007 #1
    Please help! I need these done by wednesday and for the life of me i cannot seem to get the correct answer.

    1. The problem statement, all variables and given/known data
    How much ice must melt at 0 deg. C to gain 5 g of mass?


    2. Relevant equations
    I cannot seem to find many equations that relate thermodynamics and mass, maybe that is my biggest problem... The only one i could find was
    Q=Lm


    3. The attempt at a solution
    I know the latent heat of fusion, but i do not know Q. I tried dividing both sides by L, giving me Q/L=m, but i wasn't sure where to go from there.




    1. The problem statement, all variables and given/known data
    Calculate the entropy change in isotermal transformation of ideal gas at the temperature of 27.5 deg. C if work done by the gas is 3.5 J.


    2. Relevant equations
    s(b)-s(a)=Cv*ln(Tb/Ta)+nR*ln(Vb/Va)
    pV=nRT
    dW=pdV


    3. The attempt at a solution
    since Tb/Ta=1, Cv*ln(Tb/Ta) is reduced to zero, leaving us with
    s(b)-s(a)=nR*ln(Vb/Va)
    i then attempted to use the ideal gas law combined with dW=pdV but i found myself running in circles trying to figure out what to do with p and n and trying to find Vb and Va at the same time.
     
  2. jcsd
  3. Feb 13, 2007 #2
    anyone? please this is very important and it is due at 12:00 midnight. i've tried really hard and i will continue to try but if anyone can set me in the right direction i will greatly appreciate it
     
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