A student is measuring the heat of dissolution of KNO3 in water. The student add
ID: 485672 • Letter: A
Question
A student is measuring the heat of dissolution of KNO3 in water. The student adds 4.13 g of solid KNO3to 20.15 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 24.49 oC, and the temperature of the solution after the dissolution process is complete is 13.29 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 substance = mass of KNO3 + mass of calorimeter
= 4.13g + 20.32 g
= 24.45g
specific heat =4.184 J
Difference in temperature = 24.49 - 13.29
=11.2
we know heat absorbed = mass x specific heat x difference in temperature
= 24.45 g x 4.184J/g-K x 11.2 K
= 1145.75 J
For dissolving 4.13 g KNO3 the heat of solution = + 1145.75 J
Molar heat of solution = (101/4.13) x1145.75
= +28019.55 J
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