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Chapter 4 (CIC) and Chapter 5, 8 (CTCS)

Chapter 4 (CIC) and Chapter 5, 8 (CTCS). Read in CTCS Chapter 5.1,3-4, 8.9 Problems in CTCS: 5.3, 13, 15, 22, 23, 29, 35, 90, and 8.63, 65, 67, 69. Global Warming (CO 2 )  Fuel. Fuel’s are typically fossil fuels (crude oil, coal) Gasohol is a mixture of ethanol and gasoline

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Chapter 4 (CIC) and Chapter 5, 8 (CTCS)

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  1. Chapter 4 (CIC) and Chapter 5, 8 (CTCS) • Read in CTCS Chapter 5.1,3-4, 8.9 • Problems in CTCS: 5.3, 13, 15, 22, 23, 29, 35, 90, and 8.63, 65, 67, 69

  2. Global Warming (CO2)  Fuel • Fuel’s are typically fossil fuels (crude oil, coal) • Gasohol is a mixture of ethanol and gasoline • CH2=CH2 + H2O  CH3CH2OH • C6H12O6 CH3CH2OH + CO2 • Does EtOH give same performance as gasoline? Does EtOH give the same amount of energy per gram? • 1st Law – If we have Conservation of Energy, why are worried about depleting our resources?

  3. Annual US Energy Consumption From Various Sources

  4. Combustion • All but two of those energy sources were based on combustion giving CO2 as a byproduct • Energies can be obtained from a calorimeter Q: Determine the heat of combustion for a gram of natural gas (CH4) compared to a gram of butane (C4H10) if their heats of combustion are –802.3 and –2658.4 kJ/mol respectively. A:-50.01 kJ/g and –45.74kJ/g

  5. Energy Diagram Reactants Hrxn Enthalpy Products Reaction Progress

  6. Where does the exothermic energy come from? • When bonds are broken, energy is required • When bonds are made, energy is released • Compare the bond strengths in the equation above (See Table 8.4 - pg 289) • The products are: • More stable • Lower in Energy • Have stronger bonds

  7. CO2 and H2O are too stable (have bonds that are too strong) to decompose and give off more energy Q: Could you use ozone as a fuel? How much energy is released/g of ozone? (Use bond energies to calculate) A: -2.11 J/g (-2.96 kJ/g according to Hºf) • Bond Energies are averages of gas molecules • Hºf – enthalpy of formation in standard state (º)

  8. Q: Using bond energies, calculate the heat of reaction for the combustion of molecular hydrogen and 1 mol of oxygen to form gaseous products A: -485 kJ (actual = -483.6 kJ) Q: Would you expect a more endo- or exo-thermic reaction if the products were liquid?

  9. H2O(g) H2O(l)H = negative,WHY? • 2 H2(g) + O2(g) 2 H2O(l) • Can’t use bond energies! • Hºrxn = -571.7 kJ • Spontaneity (G) • If you have a large negative H, you can assume spontaneity Q: What are some of the strongest bonds?

  10. Triple: NN, CO; Double: C=O; Single: O-H, Si-O • This suggests that these bonds would have trouble reacting 2 CO + O=O  2 O=C=O Hºrxn= -566 kJ • Explosives • Should have many weak bonds • Ideally have all atoms of reaction self contained • Need to be stable enough to work with • Should create gaseous molecules

  11. Nitroglycerin • What are the products of decomposition? Q: What is the Hrxn/mol of nitro? (why not Hºrxn?) A: -1782 kJ

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