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physicsnerd7
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Homework Statement
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.
Homework Equations
Qreleased + Qabsorbed = 0
Q = mcΔT
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 don't know!