Sarah is measuring the heat of dissolution of KNO3 in water. She adds 8.77 g of
ID: 542602 • Letter: S
Question
Sarah is measuring the heat of dissolution of KNO3 in water. She adds 8.77 g of solid KNO3 to 21.36 mL of deionized water in a coffee cup calorimeter (mass of the coffee cups + the stir bar = 20.32 g). The initial temperature of the water is 55.9 oC, and the temperature of the solution after the dissolution process is complete is 13.42 oC. Assuming the specific heat of the solution is the same as that of pure water (4.184 J/g-K), what is the heat of solution for the dissolution process in J (Joules)? Express your answer to two digits after the decimal.
Explanation / Answer
mass of KNO3 = 8.77 g
volume of water = 21.36 mL
mass of water = 21.36 x 1 = 21.36 g
mass of solution = 8.77 + 21.36 = 30.13 g
specific heat = 4.184 J / g oK
initial temoerature of water = 55.9 oC
temperature of solution after dissolution = 13.42 oC
heat Q = m Cp dT
= 30.13 x 4.184 x (13.42 - 55.9)
heat = - 5355 . 2 J
heat of solution = - 5355 J
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