When a solid dissolves in water, heat may be evolved or absorbed. The heat of di
ID: 696865 • Letter: W
Question
When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determined using a coffee Thermometer cup calorimeter. Cardboard or Styrofoam lid In the laboratory a general chemistry student finds that when 3.07 g of CaBr2(s) are dissolved in 109.30 g of water, the temperature of the solution increases from 22.12 to 25.59 °C The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be Nested 1.83 J/PC Based on the student's observation, calculate the enthalpy of dissolution of CaBr2(s) in k.J/mol. Assume the specific heat of the solution is equal to the specific heat of water. AHdissolution = Styrofoam cups Reaction occurs in solution. kJ/mol Submit Answer Retry Entire Group 9 more group attempts remainingExplanation / Answer
heat released(q) = m*s*DT + C*DT
m = mass of solution = 109.3 + 3.07 = 112.37 g
s = specific heat of solution = 4.184 j/g.c
DT = 25.59-22.12 = 3.47
q = 112.37*4.184*3.47 = 1.631 kj
no of mol of CaBr2 = w/Mwt = 3.07/200 = 0.01535 mol
DHrxn = -q/n = -1.631/0.01535 = -106.25 kj/mol
heat released(q) = m*s*DT + C*DT
m = mass of solution = 109.4+2.56 = 111.96 g
s = specific heat of solution = 4.184 j/g.c
DT = 27.01-24.1 = 2.91
q = 111.96*4.184*2.91 = 1.363 kj
no of mol of Coso4 = w/Mwt = 2.56/155 = 0.0165 mol
DHrxn = -q/n = -1.363/0.0165 = -82.6 kj/mol
from the given data
1/2*rev.eq.1 + 1/2*eq.2 = eq.3
1/2*(544.0) + 1/2*(-696.6) = DH0 of e.3
DH0 = -76.3 kj/mol
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