What are important consequences of lattice enthalpies?

How can the lattice enthalpy of an ionic NaCl be determined by using Born-Haber cycle?

Calculate the lattice enthalpy of KCl crystal from the following data:

Sublimation enthalpy of pottasium (K) = +89 kJ mol^-1
Dissociation enthalpy of 
                                          = +122 kJ mol^-1
Ionisation enthalpy of K(g) +425 kJ mol-1
Electron gain enthalpy of Cl(g) = -355 kJ mol^-1
Enthalpy of formation of 

Calculate the lattice enthalpy of LiF, given that the enthalpy of
(i) sublimation of lithium is 155.2 kJ mol^–1
(ii) dissociation of 1/2 mol of F₂is 75.3 kJ
(iii) ionization of lithium is 520 kJ mol^–1
(iv) electron gain of 1 mol of F(g) is –333 kJ
(v) ∆_f H⁰ ∆_fH⁰ overall is –795 kJ mol^–1

Calculate the lattice enthalpy of MgBr₂ from the given data. The enthalpy of formation of MgBr₂ according to the reaction

The tendency of a system to acquire a state of maximum randomness is the sole criterion for the spontaneity of a process. Comment.