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Comparing Fossil Fuel and Biofuel Combustion

Comparing Fossil Fuel and Biofuel Combustion. Short Introduction . Methane: A non-renewable fossil fuel gas pumped from deep below the Earth’s surface from both coal and oil deposits.

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Comparing Fossil Fuel and Biofuel Combustion

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  1. Comparing Fossil Fuel and Biofuel Combustion

  2. Short Introduction Methane: • Anon-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 gasolinerefined 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

  5. Calculating the Total Bond Energy of a molecule. TABLE 1: BOND ENERGY VALUES Methane: CH4

  6. Part A - Modeling Combustion Reactions 1. Use the model pieces to build each of the fuel molecules below. Draw the structural formula for each molecule. Hint: All bonds are single bonds. ETHANOL METHANE

  7. Part A - Model the combustion of methane in the presence of just enough oxygen. 1. Make the models of the reactants: one CH4 and two O2 molecules. 2. Next model the breaking of the reactant bonds by removing all the white bonds from the atom of the three reactant molecules. 3. Finally, model the formation of the products by reassembling the six bonds and seven atoms from the “broken” reactant molecules to make as many water (H2O) and carbon dioxide (CO2) molecules as you can.

  8. Part A - Model the combustion of methane in the presence of just enough oxygen. Count up the number of H2O and CO2 molecules you made and complete the chemical equation below that shows the combustion of methane. CH4 + 2O2 → CO2 + 2H2O

  9. Part A - Model the combustion of ethanol in the presence of more than enough oxygen. 1. Make the models of the reactants: one C2H6O and five O2 molecules. 2. Next model the breaking of the reactant bonds of your C2H6O and just enough (but not all) of your O2 molecules to make the products water (H2O) and carbon dioxide (CO2) molecules. Hint: If you break apart more O2 molecules than you need, reassemble them.

  10. Part A - Model the combustion of ethanol in the presence of more than enough oxygen. Determine the number of O2 molecules you needed to combust the single molecule of ethanol and count the number of water (H2O) and carbon dioxide (CO2) molecules you produced. Use this data to complete the chemical equation that describes the combustion of ethanol. C2H6O + 3O2 → 2CO2 + 3H2O

  11. Part A - Model the combustion of octane in the presence of oxygen. Octane, C8H18, has a structure very similar to methane. Draw its structural formula.

  12. Part A - Model the combustion of octane in the presence of oxygen. Below is the completed chemical equation that describes the combustion of octane. C8H18 + 12.5 O2→ 8CO2 + 9H2O

  13. Part A - Model the combustion of octane in the presence of oxygen. 1. Make the models of the reactants: one C8H18 and one O2 molecules. 2. Next model the breaking of the reactant bonds of your C8H18 and your O2 molecule to make the products 8 water (H2O) and 9 carbon dioxide (CO2) molecules.

  14. 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

  15. 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. METHANE

  16. 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. ETHANOL

  17. 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. OCTANE

  18. 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. OXYGEN

  19. 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 PRODUCT molecules. CARBON DIOXIDE

  20. 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 PRODUCT molecules. WATER

  21. Part B - Calculating the Energy Released During METHANE Combustion CH4 + 2O2 → CO2 + 2H2O Energy released = (total bond energy of products) - (total bond energy of all reactants) REACTANTS Total Bond Energy in reactants = 2646.6 kJ/mole PRODUCTS Total Bond Energy in products = 3464.2 kJ/mole

  22. Part B - Calculating the Energy Released During METHANE Combustion CH4 + 2O2 → CO2 + 2H2O Energy released = (total bond energy of products) - (total bond energy of all reactants) Products - Reactants = Energy Released 3464.2 - 2646.6 = 817.6 kJ/mole of methane combusted

  23. Part B - Calculating the Energy Released During ETHANOL Combustion C2H6O + 3O2 → 2CO2 + 3H2O Energy released = (total bond energy of products) - (total bond energy of all reactants) REACTANTS Total Bond Energy in reactants = 4725.1kJ/mole PRODUCTS Total Bond Energy in products = 5999.6 kJ/mole

  24. Part B - Calculating the Energy Released During ETHANOL Combustion Energy released = (total bond energy of products) - (total bond energy of all reactants) C2H6O + 3O2 → 2CO2 + 3H2O Products - Reactants = Energy Released 5999.6 - 4725.1 = 1274.5 kJ/mole of ethanol combusted

  25. Part B - Calculating the Energy Released During OCTANE Combustion C8H18 + 12.5O2 → 8CO2 + 9H2O Energy released = (total bond energy of products) - (total bond energy of all reactants) REACTANTS Total Bond Energy in reactants = 16,072.95kJ/mole PRODUCTS Total Bond Energy in products = 21,212.0 kJ/mole

  26. Part B - Calculating the Energy Released During OCTANE Combustion Energy released = (total bond energy of products) - (total bond energy of all reactants) C8H18 + 12.5O2 → 8CO2 + 9H2O Products - Reactants = Energy Released 21,212.0 - 16,072.95 = 5139.0 kJ/mole of octane combusted

  27. Analysis Of all the three fuels analyzed in this activity, which do you think is the best? Explain METHANE - highest energy to CO2 ratio

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