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Chemistry U3AOS1 (Fuels (Biofuels (Bioethanol: is produced by a process…
Chemistry U3AOS1
Fuels
Biofuels
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Biogas: when bacteria break down the proteins and carbohydrates of animal/plant waste into carbon dioxide and methane gas
Biodiesel: methyl esters made from vegetable oil or recycled animal fat, with methanol in a precess called transesterification
Petrodiesel
Non-renewable, can be used without additives, emissions and CO2 particulates and black soot, environmental impact of oil spills and habitat damage, dispersion forces
Non-renewable
used up faster than it can be replaced. Produced from the compression of living matter over millions of years
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Definition
substances that have lots of energy stored in their bonds, that can be released easily
Biodiesel
Renewable, likely to need antifreeze additives, emissions of CO2 but CO2 is also used in the production of triglycerides fewer particulates, environmental impact of land degradation, made on waste production, dispersion and dipole-dipole forces
Exothermic
energy is released when the new bonds are formed, enthalpy is negative
Endothermic
energy is absorbed in order to break bonds, enthalpy is positive
Specific Heat Capacity
q = m C ΔT, a measure of the amount of energy required to raise the temperature of 1g of a substance by 1 degree
Stoichiometry
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Determine the mole ratio, and use it to determine the 'unknown substance'
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Redox Reactions
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Alkaline
write acidic, cancel out H+ with OH- for H2O, balance OH- on the other side, cancel water
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Gases
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Universal Gas Equation
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P (kPa), V (L), n (mol), R (8.31), T (K)
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Galvanic Cells
Two half cells connected by an external wire and a salt bridge, indirect contract
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Flow of electrons is always from negative to positive, anode to cathode
Commercial Cells
Secondary Cell
Discharge
chemical to electrical, electrodes produce solid PbSO4 which sticks to electrolyte whcih allows recharge, OILRIG and CPRANO apply, electrons flow from (-) to (+) and ions flow (-) to (-) and (+) to (+)
Recharge
electrical to chemical, OILRIG applies but CPRANO doesn't, electrons flow (+) to (-), ions flow (-) to (+) and (+) to (-)
Fuel Cell
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However, they are expensive, it is hard to store the gases, and hydrogen is from crude oil, therefore non-renewable
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Primary Cell
Alkaline cell
Powdered zinc reacts more quickly than Zn(s) due to the larger SA:V, has a salt bridge (potassium hydroxide)
Dry cell
1-5V, low performance goes flat once Zn casing is used up, has a salt bridge (ammonium chloride jelly)