Question

Use constant-pressure calorimetry to determine the enthalpy change. When 0.660 g of MgCl2 is dissolved in 116.00 g of water, the temperature of the solution increases from 25.00 to 27.20 °C. Based on this observation, calculate the enthalpy of dissolution of MgCl2 in kJ/mol.

A) 6.04 kJ/mol
B) 3.02 kJ/mol
C) 4.12 kJ/mol
D) 2.06 kJ/mol

Answer 1

To determine the enthalpy change of dissolution, we can use the heat transferred during the process. In this case, we can apply the equation q = m*c*ΔT, where q is the heat transfer, m is the mass of the solution, c is the specific heat capacity, and ΔT is the change in temperature.

Step-by-step explanation:

To determine the enthalpy change of dissolution, we can use the heat transferred during the process. In this case, we can use the equation q = m*c*ΔT, where q is the heat transfer, m is the mass of the solution, c is the specific heat capacity, and ΔT is the change in temperature. First, we need to calculate the mass of the solution. Since the mass of the water is given as 116.00 g, and the mass of MgCl2 is 0.660 g, the mass of the solution is 116.00 g + 0.660 g = 116.66 g.

Next, we can calculate the heat transfer using the specific heat capacity of water, which is 4.18 J/g °C. Plugging in the values, we have q = (116.66 g)*(4.18 J/g °C)*(27.20 °C - 25.00 °C) = 1142.41 J. To convert the heat transfer to kJ, we divide by 1000, so the heat transfer in kJ is 1.14241 kJ. Finally, to determine the enthalpy change of the dissolution of MgCl2 in kJ/mol, we can use the molar mass of MgCl2, which is 95.21 g/mol. Dividing the heat transfer by the number of moles of MgCl2, we have (1.14241 kJ)/(0.660 g/95.21 g/mol) = 6.04 kJ/mol.