Determine the heat of sodium chloride formation based on the following data:

Udiss (Cl2) = 243 kJ/mol,

g s H(Na) = 110.0 kJ/mol,

g s H (NaCl) = 789.5 kJ/mol,

Na(g) = Na+ (g) + e- Ei(Na) = +502 kJ/mol,

Cl- (g) = Cl(g) + e- Eea(Cl) = 355 kJ/mol.