Final answer:
The lattice enthalpy of MgO is significantly higher than that of MgCl₂, as lattice enthalpy increases with the charge and decreases with the size of the ions. With Mg²⁺ and O²⁺ both having double the charge of the ions in MgCl₂, and similar sizes to LiF ions, MgO has an expected lattice energy of approximately 4008 kJ/mol, which is much higher than that of MgCl₂.
Step-by-step explanation:
The lattice enthalpies of MgCl₂ and MgO can be compared considering the charges on the ions and the sizes of the ions. Lattice enthalpy, which is a measure of the strength of the forces holding ionic compounds together, increases rapidly as the charges on the ions increase and the sizes of the ions decrease. Given that both Mg²⁺ and O²⁺ have twice the charge of the ions in MgCl₂ and considering similar ionic sizes, the lattice enthalpy of MgO is expected to be significantly higher than that of MgCl₂.
From given data, we have the lattice energy of LiF, which is 1023 kJ/mol with ions having a charge of +1 and -1, respectively. By comparison, with MgO ions both having a charge of +2 and -2 and similar ionic sizes to LiF, we can infer that the lattice energy of MgO is expected to be much higher than that of LiF. It is mentioned that the lattice energy of MgO is approximately 4008 kJ/mol, which confirms that the lattice energy of MgO is indeed substantially greater than MgCl₂, as a quadrupling of the energy is expected when the charge on the ions is doubled.