In the laboratory a \"coffee cup\" calorimeter, or a constant pressure calorimet

Question

In the laboratory a "coffee cup" calorimeter, or a constant pressure calorimeter, is frequently used to determine the specific heat of a solid, or to measure the energy of a solution phase reaction. Since the cup itself can absorb energy, a separate experiment is needed to determine the hear capacity of the calorimeter. This is known as calibrating the calorimeter and the value determined is called the calorimeter constant. One way to do this to use a common metal of known heat capacity. In the laboratory a student heats 93.31 grams of copper to 99.00 degree C and then drop it into a cup containing 79.69 grams of water at 20.87 degree C. She measures the final temperature to be 28.43 degree C. Using the accepted value for the specific heat of copper (See the References tool), calculate the calorimeter constant. Calorimeter Constant = J/degree C.

Explanation / Answer

1) Energy lost by copper metal:

q = m Cp T

q = (93.31 g) (0.376 J/g-1 °C-1) (99-28.43)°C

q = 2475.91 J

2) Energy gained by the cold water:

q = m Cp T

q = (79.69 g) (4.184 J/g-1 °C-1) (28.43-20.87) °C

q = 2520.67 J

3) The calorimeter got the rest:

=(2520.67-2475.91) J

4) Heat capacity of the calorimeter:

44.76J / (28.43-20.87)°C = 5.9J/°C

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