Question 15
Anhydrous magnesium chloride, MgCl2, can absorb water to form the hydrated salt MgCl2.4H2O
MgCl2(s) + 4H2O(l) ⟶ MgCl2.4H2O(s)
(a) Suggest one reason why the enthalpy change for this reaction cannot be determined directly by calorimetry.
(1)
(b) Some enthalpies of solution are shown in Table 1.
Calculate the enthalpy change for the absorption of water by MgCl2(s) to form MgCl2.4H2O(s).
(2)
(c) Describe how you would carry out an experiment to determine the enthalpy of solution of anhydrous magnesium chloride.
You should use about 0.8 g of anhydrous magnesium chloride.
Explain how your results could be used to calculate the enthalpy of solution.
(6)