Question

In a coffee-cup calorimeter, 11.0-g sample of solid CaCℓ2 is dissolved in 125 g of water at 25.0 oC. The temperature in the calorimeter is measured to be 39.2 oC when the dissolution of CaCℓ2 is completed. Assuming that the specific heat of solution is equal to that of water, i.e., 4.184 J/g oC, calculate the heat of solution of CaCℓ2 in water, in kJ/mol.

Answer 1

Mass of solution = (11.0 g + 125 g) = 136 g Specificheat of solution, s = 4.184 J/g °C Change in temperature AT = 39.2°C-25.0°C = 14.2°C Amount of heat absorbed in the reaction is equal to the heat relased by the calorimeter. Per = -(some) = -(m. h47) --(136gx4.184,4(14.2°c)) = -8080 J = -8.08 KJ No of moles of CaCl, = 11.0 g x= 1 mol CaCl2 = 0.0991 mol Caa, 111 g -8.08 AJ Enthalpy change, AH... = 9001 = -81.53 kJ/mol