1. Hess’s Law Start Finish A State Function: Path independent.
Both lines accomplished the same result, they went from start to finish.
Net result = same.

2. and.. the H values must be treated accordingly.
Determine the heat of reaction for the reaction:
4NH3(g) O2(g)  4NO(g) + 6H2O(g)
Using the following sets of reactions:
N2(g) + O2(g)  2NO(g) H = kJ
N2(g) + 3H2(g)  2NH3(g) H = kJ
2H2(g) + O2(g)  2H2O(g) H = kJ
Hint: The three reactions must be algebraically manipulated to sum up to the desired reaction.
and.. the H values must be treated accordingly.

3. Found in more than one place, SKIP IT (its hard).
Goal:
4NH3(g) O2(g)  4NO(g) + 6H2O(g)
Using the following sets of reactions:
N2(g) + O2(g)  2NO(g) H = kJ
N2(g) + 3H2(g)  2NH3(g) H = kJ
2H2(g) O2(g)  2H2O(g) H = kJ
4NH3  2N H2 H = kJ
NH3:
Reverse and x 2
Found in more than one place, SKIP IT (its hard).
O2 :
NO: x2
2N O2  4NO H = kJ
H2O: x3
6H O2  6H2O H = kJ

4. Found in more than one place, SKIP IT.
Goal:
4NH3(g) O2(g)  4NO(g) + 6H2O(g)
4NH3  2N H2 H = kJ
NH3:
Reverse and x2
Found in more than one place, SKIP IT.
O2 :
NO: x2
2N O2  4NO H = kJ
H2O: x3
6H O2  6H2O H = kJ
Cancel terms and take sum.
+ 5O2
+ 6H2O
H = kJ
4NH3 
4NO
Is the reaction endothermic or exothermic?

5. Consult your neighbor if necessary.
Determine the heat of reaction for the reaction:
C2H4(g) + H2(g)  C2H6(g)
Use the following reactions:
C2H4(g) O2(g)  2CO2(g) H2O(l) H = kJ
C2H6(g) + 7/2O2(g)  2CO2(g) H2O(l) H = kJ
H2(g) /2O2(g)  H2O(l) H = -286 kJ
Consult your neighbor if necessary.

6. Determine the heat of reaction for the reaction:
Goal: C2H4(g) + H2(g)  C2H6(g) H = ?
Use the following reactions:
C2H4(g) O2(g)  2CO2(g) H2O(l) H = kJ
C2H6(g) + 7/2O2(g)  2CO2(g) H2O(l) H = kJ
H2(g) /2O2(g)  H2O(l) H = -286 kJ
C2H4(g) :use 1 as is C2H4(g) O2(g)  2CO2(g) H2O(l) H = kJ
H2(g) :# 3 as is H2(g) /2O2(g)  H2O(l) H = -286 kJ
C2H6(g) : rev # CO2(g) H2O(l)  C2H6(g) + 7/2O2(g) H = kJ
C2H4(g) + H2(g)  C2H6(g) H = -137 kJ

7. enthalpy is a state function and is path independent.
Summary:
enthalpy is a state function
and is path independent.

9. Standard Enthalpies of formation:

10. Thermodynamic Quantities of Selected Substances @ 298.15 K