Question

Use constant-pressure calorimetry to determine enthalpy change,

The salt magnesium chloride is soluble in water. When 0.660 g of MgCl, 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).
Assume that the specific heat of the solution is 4.184 J/g °C and that the heat absorbed by the calorimeter is negligible
AH dissolution
kJ/mol

Answer 1

The enthalpy of dissolution for MgCl₂ is calculated by applying the formula q = mcΔT and then converting the heat absorbed to kilojoules and dividing by the number of moles of MgCl₂ dissolved.

Step-by-step explanation:

The student is asking about the calculation of the enthalpy of dissolution for magnesium chloride (MgCl₂) using a constant-pressure calorimetry experiment. To calculate the enthalpy change, we need to use the formula q = mcΔT, where q is the heat exchanged, m is the mass of the solution, c is the specific heat capacity, and ΔT is the change in temperature. Once we find the amount of heat (q) in joules, we can convert it to kilojoules by dividing by 1,000, and then use the molar mass of MgCl₂ to find the enthalpy per mole. Here is the step-by-step calculation:

1. First calculate ΔT, which is the temperature change: ΔT = 27.20°C - 25.00°C = 2.20°C.
2. Then calculate the heat absorbed by the solution: q = mcΔT = (116.00 g + 0.660 g) × 4.184 J/g°C × 2.20°C.
3. Convert q from joules to kilojoules by dividing by 1,000.
4. Find the molar mass of MgCl₂ and divide the heat (in kilojoules) by the moles of MgCl₂ dissolved to find the enthalpy of dissolution per mole.