Use the following data (all in kJ mol^-1): enthalpy of sublimation of Mg =147.7; first ionisation enthalpy of Mg =737.7; second ionisation enthalpy…

Use the following data (all in $\mathrm{kJ\,mol^{-1}}$): enthalpy of sublimation of Mg $=147.7$; first ionisation enthalpy of Mg $=737.7$; second ionisation enthalpy of Mg $=1450.7$; enthalpy of atomisation of $\mathrm{Cl}$ (per mole of Cl atoms) $=121.5$; electron gain enthalpy of Cl $=-349$; $\Delta_fH^\circ(\mathrm{MgCl_2,\,s})=-641.3$. The hypothetical compound $\mathrm{MgCl}$ (rock-salt type) is estimated to have a lattice enthalpy of $-753$. The magnitude of the enthalpy change of the reaction $\mathrm{2MgCl(s)\rightarrow Mg(s)+MgCl_2(s)}$ is ______ $\mathrm{kJ}$ per mole of $\mathrm{MgCl_2}$ formed. Give the answer correct to two decimal places.