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19 Cards in this Set
- Front
- Back
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In photosynthesis are the products more or less stable than the reactants?
CO2 + H20 = CH2O + O2 |
The reactants are less stable by 450 kJ
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How can the energy in carbohydrates be accessed?
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The energy is released when it reacts with oxygen in respiration or combustion.
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What is the opposite of photosynthesis?
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Combustion or respiration.
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So why is oil/energy found below the ground?
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There is a small amount of plant and animal matter buried beneath the ground, away from oxygen and thus it has been lying there uncombusted and can be harvested for human use. When subject to the high pressures and temperatures beneath the earth's crust, this matter became coal, oil and gas.
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In essence, what is our relationship to the solar energy of the past?
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We live off of the solar energy of the past, when we harvest those plant and animal matter that have turned into coal, oil and gas
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How are CO2 and 02 used in combustion?
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O2 is consumed while CO2 is produced
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Could we use up all the oxygen in the atmosphere if we combusted all the available fossil fuels?
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We would use up a small amount of O2. We would produce the same amount of CO2 which would have a greater impact.
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Where does petroleum and natural gas come from?
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- marine origin
- photosynthesis produces 25 - 50 billion tons of reduced carbon yearly - when this sinks to the bottom, out of reach of oxygen, anaerobic bacteria digest this, releasing oxygen and nitrogen |
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Why does petroleum and natural gas formation take millions of years in nature?
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- deposits become more deeply buried and rearrangement reactions occur as temperature and pressure rise
- methane and light hydrocarbon gas are formed in pockets - oil is produced from the heavy hydrocarbons |
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How fast could we use up these resources that took millions of years to form?
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- a century and a half
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What are gas hydrates?
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These are underwater compounds that involve a methane molecule being surrounded by hydrogen bonded water molecules.
- much more gas to be found in these hydrates |
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Where does coal come from?
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- terrestrial origin
- remains of plant matter from huge, thickly wooded swamps that flourished 250 million years ago - woody plants are mainly made of lignin and cellulose |
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Is lignin easily digested by bacteria?
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- no
- it is a complex 3 dimensional polymer based on benzene rings |
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Because lignin isn't easily digested by bacteria, what happens to it?
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It accumlates under water and compacts into peat.
- the depression and thrusting of the earth's crust subjects the peat to high temperatures and pressures changing it into hard, black, carbon-rich material we call coal |
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Where does energy come from when you break bonds?
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- Energy comes from the propensity of forming new bonds
- If the new bonds are lower in energy, they will release more energy in formation than the amount that was put in |
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How do you calculate the production of energy in a reaction?
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Calculate the energy that goes into the formation of the bonds in the product and subtract the bond formation energy of the reactants, which tells you how much net energy is released
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Which is stronger?
ionic or covalent bonds? single or double bonds? |
ionic bonds are stronger because the difference in polarity adds to the bond
double bonds are stronger and take more energy to break than single bonds |
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Why is the C=0 stronger than the 0=0?
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The C=O bond has electronegativity to contribute to greater attraction.
The O=O double bond has electron pairs on the oxygens repelling each other. In addition, both Oxygens are very electronegative |
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Why does combustion release so much energy?
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The weakness of the O=O double bond and the strength of the O-H and C=O bonds
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