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Homework Help: Entropy change of ice-water mixture at 273K

  1. Aug 4, 2011 #1
    1. The problem statement, all variables and given/known data
    A mixture of 1.773kg of water and 227g of ice is in an initial equilibrium state at 273K, in a reversible process, brought to a second equilibrium state where the water-ice ratio,by mass, is 1:1 at 273K. Calculate the entropy change of the system during the process.

    2. Relevant equations
    [tex]\Delta S=\int\limits_{i}^{f}\frac{dQ}{T}[/tex]
    specific heat of fusion of water = 333000J/kgK

    3. The attempt at a solution

    Since final mass ratio is 1:1 the final mass is both ice and water is
    m=(1.733+0.277)/2=1.025kg, which means 0.748 kg of water is turned to ice. Some water gives away energy and freezes to ice.
    [tex]\Delta E=-0.748(333000)=-249084J[/tex]
    [tex]\Delta S=-249084/273=-912J/K[/tex]
    But that is not the answer.
    Last edited: Aug 4, 2011
  2. jcsd
  3. Aug 4, 2011 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    Your method is correct. Use 334 J/g as the heat of fusion for water. I get -915 J/K

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