Hess S Law Packet

Hess’s Law Packet Name______

Period______Date______

DIRECTIONS: For each of the following problems, refer to the Heats of Reaction Table. Be sure to show all your work, including all “sub-equations” with their ΔH’s and the final “overall equation” or “net reaction” (proving additivity of reactions), calculating its ΔH.

1. Calculate ΔH for the following reaction: 2H2S + 3O2 → 2H2O(g) + 2SO2

2. How much heat is liberated when magnesium reduces carbon in CO2 to free carbon according to the following balanced chemical equation? 2Mg + CO2 → C + 2MgO

3. Calculate ΔH for the production of sulfur dioxide (SO2) according to the following balanced equation: H2SO4 → SO2 + H2O(g) + ½O2

1) -1038.0 kJ 2) -809.8 kJ 3) +273.0 kJ 1 4. This reaction occurs in our atmosphere due to pollution from burning fossil fuels containing sulfur. The sulfur in the fuel is converted to sulfur dioxide through the burning process and enters the atmosphere where it reacts with oxygen to produce sulfur trioxide (the reaction below). The sulfur trioxide then reacts with water in the atmosphere to produce sulfuric acid or acid rain.

Calculate the ΔH for the reaction of sulfur dioxide with oxygen to produce sulfur trioxide according to the following balanced equation: 2SO2 + O2 → 2SO3

5. Calculate ΔH for the following unbalanced equation for the burning of ethane (a constituent of natural gas.) C2H6 + O2 → CO2 + H2O(g)

6. Calculate the enthalpy (ΔH) for the following reaction. Ca(OH)2(s) → CaO(s) + H2O(l)

4) -198.0 kJ 5) -2858.8 kJ 6) +65.3 kJ 2 7. Calculate ΔH for the following unbalanced equation. Cl2 + HBr → HCl + Br2

8. Nitric oxide may be burned as a fuel according to the following unbalanced equation. A) Calculate the ΔH. NO + O2 → NO2

B) Ammonia (NH3) may be burned as a fuel according to the following unbalanced equation. Calculate the ΔH for the following reaction. NH3 + O2 → NO2 + H2O(g)

7) -113.0 kJ 8A) -112.8 kJ 8B) -1132.0 kJ 3 9. Calculate the ΔH for the burning of benzene, C6H6, from the following unbalanced equation. C6H6 + O2 → CO2 + H2O(g)

10. Calculate the heat of reaction (ΔH) for: Fe2O3 + 3CO → 2Fe + 3CO2

9) -6277.2 kJ 10) -26.5 kJ 4