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. A chunk of platinum weighing 19.73 grams and originally at 98.22 °C is dropped into an insulated cup containing 80.13 grams of water at 20.32 °C. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.60 J/°C. Using the accepted value for the specific heat of platinum (See the References tool), calculate the final temperature of the water. Assume that no heat is lost to the surroundings. Tfinal = °C.

Explanation / Answer

Q = ( m Cp dT ) metal

( m Cp dT ) metal   = ( m Cp dT ) water + (Cp dT) calorimeter

19.73 x 0.133 x (98.22 - T) = [ 80.13 x 4.184 + 1.60 ]   (T - 20.32)

2.624 x (98.22 - T) = 336.86 (T - 20.32)

(98.22 - T)   = 128.4 (T - 20.32)

98.22 - T = 128.4 T - 2609.64

2706.86 = 127.4 T

T = 21.25 oC

Tfinal = 21.25 °C.

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