1. Fe2O3(s)+ Al(s) → Al2O3(s)+ Fe(s)
DH=
-850kJ
Redox, Single Replacement …..called the Thermite Reaction
Formation Reaction: the formation of one mole of a substance from it’s elements in their standard states.
2Fe(s) + 3/2 O2(g) → Fe2O3(s) DH= -826kJ
Standard Heats of Formation are easily found!
Fe2O3(s) →2Fe(s) + 3/2 O2(g) DH= 826kJ
2Al(s) + 3/2 O2(g) → Al2O3(s) DH= -1676kJ
Fe2O3(s) + 2Al(s) → Al2O3(s) + 2Fe(s)

2. 3NO2(g)+ H2O(l) → 2HNO3(aq)+NO(g)
Write formation reaction equations for all of the substances that aren’t elements in their standard states….look up the DH’s associated with those reactions…properly manipulate them and determine DH for the main reaction.