Which pair of compounds is listed in order of increasing (more
exothermic) lattice energy?
Answer : LiF < MgO
Lattice energy depends on the charge of the constituent ions. In
MgO, the charge of cation and anion are +2 and -2 respectively.In
LiF, the charge of cation and anion are +1 and -1. Similarly, if
the electronegativity of the anion is higher, the higher will be
the lattice energy. Also, an ionic compound with smaller cation
size will have higher lattice energy.
Here, the correct order is,
LiF > LiI
NaCl > KCl
MgO > CsCl
CaO > BaCl2
LiF < MgO