Chem 1100 Lecture 10Outline of Last Lecture I. StoichiometryII. Other Greenhouse GasesIII. Effects of Greenhouse GasesIV. Energy, Work, & HeatOutline of Current Lecture I. CombustionII. Bond EnergyIII. Useful ReactionsCurrent LectureI. Combustiona. Rapid combination with O2 - Reactants + O2  products + heat - PE of reactantsmust be greater than PE of products. Otherwise there is no reaction. The difference in energy is given off as heat. b. Methane combustion: CH4 + 2O2  CO2 + 2H2) + Heat . This is an exothermic reaction (releases heat) How much heat does it release? c. Heat of Combustion: energy given off upon combustion of a specific amount of a substance. We could burn 1 mol of methane about 16 grams of methane  802.3 kJ. The heat of combustion of methane is 802.3 kJ. Heat is given off and because of that the products have less potential energy than the reactants. d. The system (CH4) loses energy/giving off heat. The energy change is going to be negative. -802.3 kJ/mol. e. On a molecular level bonds are being broken and formed. Broken = energy absorbed. Formed = energy released. If E released is greater than E absorbed then an exothermic reaction occurs. f. Bond energy – depends on the atoms sharing electrons which are broken and which are formed. Methane: Break 4 Carbon-hydrogen bonds, 2 oxygen-oxygen double bonds. Make: 2 carbon oxygen double bonds and 4 oxygen hydrogen bonds.g. Products: stronger bonds than reactants. Reactions proceed toward more stable species.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Bond Energy a. Endothermic: These reactions occur but need outside energy to go.b. We will mainly focus on exothermic reactions.c. Bond energy: energy needed for breaking a specific bond. Ex: O-H is 467 kJ/mol-How many bonds are we actually breaking?d. Bonds broken minus bonds formede.f. Good Fuels: We want to see a large energy change (exothermic). Reactants: weakbonds. Products we want strong bonds. H2O and CO2: are poor fuels (combusted). The bonds O-H and C=O are strong. They can’t be converted to stronger bonds. g.III. Usefull Reactionsa. We don’t want them to be too fast or too slow. Too slow: energy release takes too long example – rotting woodb. Too fast: explosion – difficult to control (H-bomb)c. Optimizing Reactions: increasing ratei. Maximize surface area (stirring a solution)ii. Raise temp (add energy to the system)iii. Catalysts (lower activation energy without being consumed)d. There’s no fuel like an old fuel – sunlight in plants is stored energye. 2800 kJ + 6CO2 + H20  6O2 + C6H12O6 (glucose)f.g. Coal i. Is a lot better than wood. It yields more energy per gram. 2-3x more. ii. Why? – its not a chemical compound, we can have a rough chemical formula for it. It’s almost a 100% carbon, which means you get more energy. The advantages are that there is a large supply, its widely used, especially by lesser developed nations, its more efficient than wood, and it doesn’t need processing. iii. Some drawbacks of coal – difficult to get to, its deep in the ground, there are mining accidents and health risks to workers, to make it safe is very expensive, strip mining causes erosion to the land, and its difficult to transport because you cant exactly have a coal pipeline. Low quality coal can cause pollution with carcinogens, acid rain, green house gases, and mercury. It’s anthracite: running low!iv. The Future of coal: petroleum will run out 1st, demand for coal will rise, will need refinement to make it cleaner, and cost will