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 student heats 65.43 grams of zinc to 97.79 °C and then drops it into a cup containing 78.74 grams of water at 21.61 °C. She measures the final temperature to be 27.20 °C. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.88 J/°C. Assuming that no heat is lost to the surroundings calculate the specific heat of zinc. Specific Heat (Zn) =__________ J/g°C.

Explanation / Answer

Let the specific heat be S J/g°C.

Energy lost by Zn = 65.43 * S * (97.79 - 27.20) = 4618.70*S Joules

Energy gained by water = 78.74*4.186*(27.20 - 21.61) = 1842.50 Joules

Energy consumed by calorimeter = 1.88*(27.20 - 21.61) = 10.51 Joules

Total energy lost = Total energy gained

=> 4618.70*S = 1842.50 + 10.51

=> S = 0.40 J/g°C

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