A calorimeter contains 143 g of water at 22.5°C. A 12 g sample of NaCl is added to the water in the calorimeter. After the solid has dissolved, the temperature of the water is 21.6°C. Calculate the enthalpy of solution for dissolving sodium chloride. Assume that no heat is lost to the calorimeter or the surroundings and that the specific heat of the solution is the same as that of pure water.

Question

Quizplus · Accepted Answer

The enthalpy change can be calculated using q = mcΔT, where m is the mass of the solution, c is the specific heat capacity, and ΔT is the temperature change. The mass of the solution is 143 g + 12 g = 155 g. The specific heat capacity of water is 4.18 J/g°C. The temperature change is 21.6°C - 22.5°C = -0.9°C. Thus, q = 155 g * 4.18 J/g°C * (-0.9°C) = -583.11 J. Converting to kJ gives -0.583 kJ. The molar mass of NaCl is 58.44 g/mol, so 12 g is 0.205 mol. The enthalpy of solution per mole is -0.583 kJ / 0.205 mol = -2.84 kJ/mol, which is approximately 2.8 kJ/mol.

A Calorimeter Contains 143 G of Water at 22