1. Comparing Fossil Fuel and Biofuel Combustion

2. Short Introduction Methane:
A non-renewable fossil fuel gas pumped from deep below the Earth’s surface from both coal and oil deposits.
A major component of biogas - a renewable fuel that is produced from decaying plant and animal manure.
Ethanol:
Renewable liquid biofuel produced from several different types of plant material.
Octane:
A non-renewable liquid fossil fuel which is the major component of gasoline refined from crude oil.

3. A Quick Review
Carbon-based fuels such as wood, coal, and gasoline supply energy.
These fuels release exothermic energy during a combustion chemical reaction.
The energy has been stored within the bonds of the molecules.
The energy is released because the chemical bond energy of the products are less than the chemical bond energy of the reactants.
The products of most combustion reactions include water and carbon dioxide

4. Bond Energy between two atoms
Use the information in Table 1 to determine the energy in the bonds of each of the different molecules.
TABLE 1: BOND ENERGY VALUES
Bond
Energy (kJ/mole)
C - H
414.2
C - C
347.3
O - H
464.4
Bond
Energy (kJ/mole)
C - O
357.7
H - H
439.4
Bond
Energy (kJ/mole)
C = O
803.2
O = O
494.9

5. Calculating the Total Bond Energy of a molecule.
TABLE 1: BOND ENERGY VALUES
Structural
Formula
Bond Type
Bond Energy
(kJ/mole)
# bonds in the molecule
Total Bond Energy
Methane: CH4

6. Part B - Calculating the Energy Released During Combustion Reactions
Use the information in Table 1 to determine the energy in the bonds of each of the different reactant molecules.
TABLE 1: BOND ENERGY VALUES
Bond
Energy (kJ/mole)
C - H
414.2
C - C
347.3
O - H
464.4
Bond
Energy (kJ/mole)
C - O
357.7
H - H
436.0
Bond
Energy (kJ/mole)
C = O
803.3
O = O
497.9

7. PART 2: Calculating release energy
CH O2 → CO2 + H2O

8. Part B - Calculating the Energy Released During METHANE Combustion
Energy released = (total bond energy of products) - (total bond energy of all reactants)
CH O2 → CO H2O
REACTANTS
Molecule
Bond energy per molecule (kJ/mole)
# of molecules
Total bond energy (kJ/mole)
CH4
1656.8 1 O2
497.9 2
995.8
Total Bond Energy in reactants = kJ/mole
PRODUCTS
Molecule
Bond energy per molecule (kJ/mole)
# of molecules
Total bond energy (kJ/mole)
CO2
1606.4 1
H2O
928.8 2
1857.6
Total Bond Energy in products = kJ/mole