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

Question

hemma 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 93.77 grams of lead to 99.35 °C and then drops it into a cup containing 82.18 grams of water at 22.34 °C. She measures the final temperature to ?? 25-53 °C. Using the accepted value for the specific heat of lead (See the References tool),calculate the calorimeter constant. Calorimeter Constant Submit Answer Retry Entire Group 8 more group attempts remaining

Explanation / Answer

ANSWER:

The problem can be solved b the following equality:

Heat lost by the hot lead = heat gained by calorimeter (Coffee cup)

Heat lost by the hot lead = mass of the lead (mPb) X specific heat of lead(cPb) X teperature change (Tf - Ti = ?TPb)

Similarly heat gained by the calorimeter = (mcal X ccal X ?Tcal)

mPb X cPb X ?TPb = mcal X ccal X ?Tcal

ccal = mPb X cPb X ?TPb / mcal  X ?Tcal = 93.77 X 0.127J/g X (99.35oC - 25.53oC) / 82.18g X (25.53oC - 22.34oC)

ccal = 93.77 X 0.127J/g X 73.82oC / 82.18g X 3.19oC = 3.48J/g

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