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

Question

In the laboratory a "coffee cup" calorimeter, or 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 heat 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 is to use a common metal of known heat capacity. In the laboratory a student heats 98.96 grams of nickel to 99.38 °C and then drops it into a cup containing 79.34 grams of water at 20.98 °C. She measures the final temperature to be 30.10 °C. Using the accepted value for the specific heat of nickel (See the References tool), calculate the calorimeter constant. Calorimeter Constant = J/°C.

Explanation / Answer

Heat lost by nickel = mCpdT

                              = 98.96 x 0.440 (99.38-30.10)

                              = 3016.6175 J

heat gained by water = mCpdT

                                  = 79.34 x 4.184 (30.10 - 20.98)

                                  = 3027.4621 J

Heat gained by calorimeter = 3027.4621 - 3016.6175

                                            = 10.8446 J

calorimeter constant = 10.8446 J/9.12 oC

                                  = 1.20 J/oC

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