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Homework Help: Thermodynamics and Entropy- reservoir and block problem

  1. Sep 14, 2011 #1
    1. The problem statement, all variables and given/known data
    A 382 g block is put in contact with a thermal reservoir. The block is initially at a lower temperature than the reservoir. Assume that the consequent transfer of energy as heat from the reservoir to the block is reversible. Figure 20-22 gives the change in entropy ΔS of the block until thermal equilibrium is reached. The scale of the horizontal axis is set by Ta = 280 K and Tb = 520 K. What is the specific heat of the block?



    NewPicture3.jpg


    2. Relevant equations
    ΔS= mCspln(T/To)


    3. The attempt at a solution
    ΔS= mCspln(T/To)

    Csp=ΔS/(m*ln(T/To))

    where
    ΔS= 100 J/K
    m= .382 kg
    T=520K
    To=280K

    plug and chug,
    Csp= 100/(.382*ln(520/280)) =422.88J/K*kg

    where did I go wrong ):
     
  2. jcsd
  3. Sep 15, 2011 #2
    your T0 is not Ta

    look carefully at the graph^^
     
  4. Sep 17, 2011 #3

    Ohhhhh my gosh this is why i miss points on exams lol! Thanks c:
     
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