Final answer:
The lattice energy of NaCl, Hlattice = -788 kJ/mol, represents the heat released during the crystallization process when gaseous Na+ and Cl- ions combine to form solid NaCl.
Step-by-step explanation:
The value of Hlattice for NaCl being -788 kJ/mol represents the amount of energy released when one mole of NaCl solid forms from its constituent gaseous ions. Specifically, this relates to when one mole of gaseous Na+ and Cl- ions combine to form one mole of solid NaCl, 788 kJ of energy is released. Therefore, the correct answer is that the lattice energy represents c) Heat released during crystallization. In some texts, lattice energy might be defined differently, giving a positive value and relating to the energy required to separate the solid into gaseous ions, but in this case, we are adhering to the conventional definition where a negative value indicates the release of energy.