When a solid dissolves in water, heat may be evolved or absorbed. The heat of di
ID: 932041 • 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 cup calorimeter.
In the laboratory a general chemistry student finds that when 12.05 g of BaBr2(s) are dissolved in 108.30 g of water, the temperature of the solution increases from 23.18 to 25.13 °C.
The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be1.68 J/°C.
Based on the student's observation, calculate the enthalpy of dissolution of BaBr2(s) in kJ/mol.
Assume the specific heat of the solution is equal to the specific heat of water.
Hdissolution = _______ kJ/mol
Explanation / Answer
q released = m*s*DT + cp*DT
= 12.05*4.18*(25.13-23.18)+1.68*(25.13-23.18)
= 101.5 j
= 0.1015 kj
No of mol of BaBr2 = 12.05 / 297.1350 = 0.04 mol
enthalpy of dissolution of BaBr2(s) = 0.1015/0.04 = 2.5375 kj/mol
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