Lattice enthalpy is a measure of the energy released or absorbed when gaseous ions are arranged into a solid ionic lattice. It is typically expressed in units of kilojoules per mole (kJ/mol).
The lattice enthalpy of MgCl2 can be calculated using Hess's Law, which states that the total enthalpy change for a reaction is independent of the pathway taken. In this case, the lattice enthalpy can be calculated by subtracting the enthalpy of formation of gaseous MgCl2 from the enthalpy of formation of solid MgCl2.
The lattice enthalpy of MgCl2 is affected by the charge of the ions, the size of the ions, and the distance between the ions in the crystal lattice. A higher charge or smaller size will result in a stronger lattice enthalpy, while a larger distance between ions will result in a weaker lattice enthalpy.
The lattice enthalpy of MgCl2 is exothermic because energy is released when the gaseous ions come together to form a solid crystal lattice. This energy is released in the form of heat, resulting in a negative enthalpy value.
The lattice enthalpy of MgCl2 is stronger than many other ionic compounds due to the high charge and small size of the ions. However, it is weaker than the lattice enthalpy of compounds with smaller ions, such as LiF or MgO.