# Unit 1:Developing Fuels

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Number of moles in a volume of gas
Volume in dm3 / 24 or volume in cm3 / 24000
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Enthalpy Change
Delta(triangle)H. The heat energy transferred in a reaction at constant pressure (KJ mol-1) standard conditions=298 K and 100 kPa.
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Why is enthalpy change under standard conditions
Changes are affected by temperature and pressure, so using standard conditions means everyone knows exactly what the enthalpy change is describing.8
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Exothermic
Bond making. Many energy is given out than taken in. ∆H is negative
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Endothermic
Bond breaking. More energy is taken in than given out. ∆H is positive
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Standard enthalpy change of combustion
∆Hc with subway sign, the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions. Exothermic = negative results
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Standard enthalpy change of reaction
∆Hr with subway sign, the enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation, under standard conditions in their standard states. Exothermic = negative results
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Standard enthalpy change of formation
∆Hf with subway sign, the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions. Exothermic = negative results
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Neutralisation
add a known volume of acid to an insulated container + measure temp. Then add known volume of alkali, and record temp rise. q(heat loss/gained) = m(mass g)xc(4.18Jg-1K-1)∆T(change in temp)
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Enthalpy combustion of a flammable liquid
Stirrer and thermometer in the water in the insulated container. Put the fuel in the combustion chamber with the air supply. As the fuel burns, it heats the water, but some will get lost to it's surroundings.
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Limitations of card 9 + 10
some heat gets absorbed by container/lost to surroundings. Some combustion may be incomplete - less energy given out. Some flammable liquid may escape by evaporation - usually volatile.
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Calculating enthalpy changes from experimental results
1) q=mc∆T 2) N=mass/Mr 3) answer from 1/2
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Hess's Law
Total enthalpy change of a reaction is the same, no matter which route is taken. Route 1 + Route 2
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Bond enthalpy
The energy needed to break a bond or the energy given out when a bond forms.
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Bond enthalpy's relation to the length and strength
The stronger the attraction between the atoms, the higher the bond enthalpy and the shorter the bond length. If there's more attraction, the nuclei pulls closer together. Double bonds have higher bond enthalpy than single, triple higher than double..
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Entropy
Measure of the number of ways that particles can be arranged - a measure of disorder.
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Entropy of a solid, Liquid and Gases
S-Particles don't move freely, they wobble about a fixed point, so it's easy to predict where a particle's going to be. L- particles are close but can move freely, so harder to predict. G-particles far apart, no order its random so unpredictable
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Catalyst
Speeds up a chemical reaction but can be recovered chemically unchanged at the end of the reaction.
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Catalysis
Speeding up a chemical reaction by using a catalyst
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Catalyst Poison
When poisoned, don't work. CO poisons solid iron catalyst in Haber Process. Lead poisons catalytic converters in car exhausts. Heterogenous catalysts often poisoned as it sticks to surface more than reactant, so can't get involved + speed reaction up
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Heterogenous
Catalysts in different physical state from the reactants. Iron in Haber Process is solid + reactants are gas.
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Catalysts in Isomerisation
Sometimes, branched better than straight-chained isomers. Straight-chain alkane heated with platinum catalyst stuck on inert AlO. Molecule broken up + repaired as branched-chain isomer. Straight-chains then go through molecular sieve-zeolite+recycled
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Reforming
Converts alkanes into arenes (aromatic hydrocarbons) using a catalyst - platinum stuck on aluminium oxide
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Cracking
Breaking long-chain alkanes into smaller hydrocarbons. Zeolite catalyst at slight pressure and high temp-450 degrees. For motor fuels and aromatic hydrocarbons. Cheaper as quicker and less pressure needed.
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Formation of Carbon Monoxide
If lack of O2, hydrogen combusts incompletely creating CO.
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Greenhouse Effect
Earth warms up, as sun radiates infra red, GHG absorb some of it, making earth warmer.
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Unburnt hydrocarbons and oxides of nitrogen
Some unburnt hydrocarbons come out of engine. Oxides of Nitrogen made when high pressure and temp in engine makes nitrogen and oxygen in air react. Hydrocarbons and NO react in sunlight = ground-level ozone (O3) Causing photochemical smog
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Sulfur Dioxide
Fossil fuels containing sulfur are burned, producing sulfur dioxide that gets into atmosphere, dissolves in moisture and turns to acid rain. Destroying trees, corroding buildings and killing fish.
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Methods to stop this from society
Calcium oxide in flues-removes sulfur dioxide. Catalytic converters in engines. Change laws to reduce pollution. Tax pollution more highly.
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Crude oil
Consists of a mixture of compounds, mainly hydrocarbons, that can be seperated by fractional distillation.
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Members of homologous series
Alkanes, Cycloalkanes, Alkenes, Arenes, Alcohols and Ethers
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Members of Alkanes
CnH2n+2, -ane = Methane, Ethane, Methylpropane. Aliphatic Compound
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Members of Cycloalkanes
CnH2n, cyclo- -ane = Cyclohexane... Aliphatic Compound
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Members of Alkenes
CnH2n, -ene = Propene, Cyclopentene... Aliphatic Compound
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Members of Arenes
Benzene = Ethylbenzene Aromatic Compound.
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Members of Alcohols
CnH2n+1OH, -ol = Propan-1-ol, ethanol
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Members of Ethers
Oxygen atom interrupts carbon chain. Alcohols and ethers can be isomers of each other. Alkoxy- = methoxypropane
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Aromatic Compound
Hydrogen compound having a closed ring of alternate single and double bonds with delocalized electrons
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Aliphatic Compound
Hydrogen compound having a closed ring of single bonds with delocalized electrons
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Saturated
Single covalent bonds
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Unsaturated
At least one double covalent bonds
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Systematic nomenclature
1) count carbon atoms in largest continuous chain, 2) Main functional group goes at end 3) Write carbon number before functional group 4) Any side chains at beginning, in alphabetical order 5) If 1+ identical side-chains, use di, tri etc
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Skeletal formula
Shows bonds of carbon skeleton only, with any functional group
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Displayed formula
Shows how atoms are arranged and all bonds in between
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Structural formula
Shows atoms carbon by carbon, with functional groups attached
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Molecular formula
Actual number of atoms of each element with any functional groups
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General formula
Describe any member of a family of compounds
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Electron repulsion single bonds
Electron pairs repel each other. Carbon atom-4 single bonds, angles between the 2 covalent bonds are 109.5. Wedges and dotted lines are used to show this.
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Electron repulsion double bonds
Attached atoms are at corners.
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Structural isomers
Take away one carbon atom, add it to another carbon atom, add hydrogens accordingly.
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Octane number
The tendency of petrol to auto-ignite, causing 'knocking' in the engine-ignites twice, once due to high pressure + also when spark ignites petrol, causing damage to engine. Based on scale: isooctane=100 and heptane=0 (easily ignites under pressure
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Effect on chain length and branching on octane number
Longer the carbon chain=Lower octane rating. More carbon chain branching=Hgher octane rating. The higher the number, the less likely it is to auto-ignite, so more efficient. = High is Good!
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Renewable fuels
Wind, Solar, Wave power. Carbon neutral, no GHG. Not reliable, lots of solar panels, turbines etc to get energy.
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Biofuels
Produce CO2 but plants they're made from absorb it so still carbon neutral. Expensive to make atm. Land used to grow them could be used to grow foods.
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Nuclear Power
Nuclear fission creates no air pollution. But mining+refining uranium ore, and building plants creates CO2. Radioactive waste made and hard to deal with. Fears of nuclear disaster.
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Hydrogen
Burned or used in fuel cell. Taken from seawater-energy needed to get it. Highly flammable, has to be liquified due to low energy to volume ratio.
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## Other cards in this set

### Card 2

#### Front

Delta(triangle)H. The heat energy transferred in a reaction at constant pressure (KJ mol-1) standard conditions=298 K and 100 kPa.

Enthalpy Change

### Card 3

#### Front

Changes are affected by temperature and pressure, so using standard conditions means everyone knows exactly what the enthalpy change is describing.8

### Card 4

#### Front

Bond making. Many energy is given out than taken in. ∆H is negative

### Card 5

#### Front

Bond breaking. More energy is taken in than given out. ∆H is positive