Answer
$Pb(s) + N_2(g) + 3O_2(g)--> Pb(NO_3)_2(s)$
$\Delta H ^o _ f (Pb(NO_3)_2(s)): -451.9 kJ/mol$
Work Step by Step
1. Write the unbalanced equation:
$Pb(s) + N_2(g) + O_2(g)--> Pb(NO_3)_2(s)$
2. Balance it:
$Pb(s) + N_2(g) + 3O_2(g)--> Pb(NO_3)_2(s)$
3. The $\Delta H ^o _f$ values are found in the book's final pages.