Calculate the lattice energy for NaF (s) given the following
sublimation of energy +109 kj/mol
Hf for F (g) + 77 kj/mol
first ionization energy of Na (g) +495
electron affinity of F(g) -328
enthalpy of formation of NaF(s) -570 kj/mol
A. -177
B. 192
C. -804
D. -1047
E. -923
Na + 1/2 F2 -------> NaF H = -570Kj/mole
this reaction takes place five different steps
sublimation of energy +109 kj/mol
Na(s) --------> Na(g) H1 = 109Kj/mole
first ionization energy of Na (g) +495
Na(g) ---------> Na+ + e- H2 = 495Kj/mole
bond energy of F2
F2 ------> 2F = H = 155Kj/mole
1/2F2 -----> F = H3 = 155/2 = 77.5Kj/mole
electron affinity of F(g) -328
F + e- -------> F- H4 = -328Kj/mole
latticw energy
Na+ + F- -------> NaF H5 =
H = H1 + H2 + H3 + H4 + H5
-570 = 109 +495 +77.5 -328+H5
H5 =-923KJ/mole
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