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Homework Help: Calorimeter Cup Problem!

  1. Dec 4, 2013 #1
    1. The problem statement, all variables and given/known data
    A copper calorimeter cup with a mass of 0.27 kg contains 0.125 kg of water. At 17°C. If 95g of an unknown substance at 93°C is placed into the cup, the temperature increases to 35°C. Find the specific heat capacity of the unknown substance.

    2. Relevant equations
    Qreleased + Qabsorbed = 0
    Q = mcΔT

    3. The attempt at a solution
    So i did:
    -Qunknown substance (us) = Qwater + Qcup

    - muscus (Tf us - Ti us) = mww cw (Tfw- Tiw )+ mc cc (Tfc-Tic)

    -(0.095kg) cus (35 C - 93C) = (0.125 kg) (4.2E3 J/kgC) (35 C -17C) + (0.27 kg)(3.9E2 J/kgC) (35C-17C)

    cs = ((0.125 kg) (4.2E3 J/kgC) (35 C -17C) + (0.27 kg)(3.9E2 J/kgC) (35C-17C)) / -(0.095kg)(35 C - 93C)

    cs= 11345.5 / 5.51

    cs = 2059 J/kgC

    Okay so that is my answer (2059 J/kgC)and I would just like clarification if my answer is right because before i did it a different way and didnt inlcude the copper cup in the Qabsorbed so i got this :

    - muscus (Tf us - Ti us) = mww cw (Tfw- Tiw )

    -(0.095kg) cus (35 C - 93C) = (0.125 kg) (4.2E3 J/kgC) (35 C -17C)

    cs= ((0.125 kg) (4.2E3 J/kgC) (35 C -17C)) / -(0.095kg)(35 C - 93C)

    cs= 1715.06J/kgC

    I believe this answer is wrong!! but i dont know!
  2. jcsd
  3. Dec 5, 2013 #2


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    Science Advisor
    Homework Helper
    Gold Member

    I haven't checked your answer but it's reasonable to include the effect of the copper cup.
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