Sarah is measuring the heat of dissolution of KNO3 in water. She adds 5.87 g of
ID: 1090356 • Letter: S
Question
Sarah is measuring the heat of dissolution of KNO3 in water. She adds 5.87 g of solid KNO3 to 25.77 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 28.17 oC, and the temperature of the solution after the dissolution process is complete is 6.43 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. Do not use any sign (i.e. +/-) or unit (i.e. J) in your answer.
Explanation / Answer
we have the formula of the Heat of dissolution as,
q = m * s * dT
q = heat of solution
m = mass of the substance + mass of the water
s = specific heat of solution = 4.184 J/g.K
dT = change in temperature of solution = (28.17+273) - (6.43+273) = 21.74 K
Mass of water 25.77 g (from density of water 1g/mL)
Q = (5.87 + 25.77) * (4.184) * (21.74)
q = 2877.979 J
q = 2.9 * 10^3 J
q = 2.9 kJ ( for 2 significants)
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