The following reaction is endothermic.
2 NaNO3(s)2 Na(s) + N2(g) + 3 O2(g) ΔH(1) = 934 kJ
Calculate the enthalpy change for the reaction of the elements to form one mole of NaNO3(s).
Na(s) + 1/2 N2(g) + 3/2 O2(g)NaNO3(s) ΔH(2) = kJ
Show Approach
This will get you started but it isn't complete by any means.You may want to read up on Hess' Law. You can find many examples on the web.
First you will want Na(s) ==> Na(g) dH = ? (sublimation)
Then Na(g) ==> Na^+ + e.........ionization potential
O2 ==> 2O...........................breaking O-O bond
etc.