12201 19 The lattice enthalpy of magnesium chloride is 2493 kJ mol−1 and that of calcium chloride is 2237 kJ mol−1. (a) (i) Write an equation, including state symbols, for the lattice enthalpy of calcium chloride. [2] (ii) Explain why the lattice enthalpy of magnesium chloride is greater than that of calcium chloride. [1] (b) (i) The enthalpy of solution of magnesium chloride is −155 kJ mol−1. Complete the following enthalpy diagram for dissolving magnesium chloride. MgCI2(s) [2] 12201 [Turn over (ii) Calculate the enthalpy of hydration of magnesium ions. The enthalpy of hydration of chloride ions is −364 kJ mol−1. [2]