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Finding change in entropy

  1. Jun 16, 2013 #1
    In 250gr water at 23 oC(degrees celsius) we throw in 27gr ice at 0 oC. Find the change in entropy.
    (sorry if that was a bad translation but English is not my native language)
    The answer is 0.78 calories/oC. But I'm not sure how do this. The formula I have for entropy is: S=δQ/T

    I find the final temperature like this: (q lost in water = q gained in ice)
    m1 * 4.184 * (23 - ft) = m2 * 4.184 * (ft - 0)
    ft = 20.75 oC

    Now how do I find δQ?
  2. jcsd
  3. Jun 16, 2013 #2

    Andrew Mason

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    The formula for change in entropy between two states is: dS = dQrev/T or ΔS = ∫ dQrev/T

    where dQrev is the heat flow over a reversible path between those states.

    Before you can raise the temperature of the ice, you first have to melt it. What is the heat required to melt 27 g of ice?

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