A coffee-cup calorimeter is used to determine the heat of reaction for the react
ID: 551818 • Letter: A
Question
A coffee-cup calorimeter is used to determine the heat of reaction for the reaction of compound A with compound B.
A(aq) + B(aq) C(aq)
When we add 17.94 mL of 0.169 M A at 24.322°C to 17.94 mL of 0.169 M B already in the calorimeter at the same temperature, the resulting temperature is observed to be 33.145°C. The heat capacity of the calorimeter has previously been determined to be 32.0 J/°C. Assume that the specific heat of the mixture is the same as that of water, 4.184 J/g·°C, and that the density of the mixture is 1.00 g/mL.
How much heat, in joules, was released by the reaction?
Determine the H for the reaction per mole of reaction.(Sign is important to show if the reaction is endothermic or exothermic.)
Explanation / Answer
total mass= 17.94 * 2 = 35.88 g
Qsln = m*C*(Tf-Ti)
Qsln = 35.88 * 4.184 * (33.145-24.322) = 1324.52
QCal = Ccal*(Tf-Ti) = 32*(33.145-24.322)= 282.336
QRxn = -Qsln - Qcal
Qrxn =-1324.52 -282.336
Qrxn = -1606.856 J (heat released by reaction)
HRxn = QRxn/n
mol = MV = 17.94*0.169 = 3.03186 mmol
HRxn = (-1606.856 )/3.03186
HRxn = -529.99 kJ/mol
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