Developing Fuels OCR Chemistry Salters B F331

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Chemistry Notes
Developing fuels
Exothermic reactions give heat out to the environment and have a negative H.
Endothermic reactions take heat in from the environment and so have a positive H.
Standard Enthalpy Change Of Combustion is the energy released when one mole burns in
standard conditions
Standard Enthalpy change of Reaction is the energy needed to react molar quantities
together.
Standard Enthalpy change of formation is the energy needed to create 1 mole of a
substance
H is measured by finding the temperature change in a reaction. Use the equation Q=MCT.
Q=energy change. Then H=Q/Number of moles. Limitations include heat loss to surroundings,
incomplete combustion and evaporation of fluid.
Hess law: The total energy change does not depend on route taken
Bond enthalpy is the quantity of energy required to break a 1 mole of a specific bond and depends
on the length and strength of the bond. Breaking bonds is endothermic, making bonds is
exothermic.
Catalysts speed up the reaction but can be chemically recovered at the end of the reaction. They can
be poisoned when a substance covers the surface of a catalyst preventing it from catalysing
reactions. Heterogeneous Catalysis occurs when the catalyst is in a different state to the reactants.
Here the reactants are adsorbed onto the catalyst surface. The reactant bonds weaken. New
product bonds are formed. The product is desorbed.
Aliphatic does not contain a benzene ring
Aromatic contains a benzene ring
Saturated no double bonds
Unsaturated contains a double bond
Saturated or unsaturated Aliphatic or aromatic Other Elements
Alkanes Saturated Aliphatic No
Alkenes Unsaturated Aliphatic No
Cycloalkanes Saturated Aliphatic No
Arenes Unsaturated Aromatic No
Alcohols NA NA OH
Ethers NA NA O
Crude oil is mainly made up of by a mixture of hydrocarbons. These can be separated by fractional
distillation. Hydrocarbons consist of hydrogen and Carbon only.

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Chemistry Notes
For naming: Meth- Eth- Prop- But-. If it is an alcohol contains an ­ol. They contain O then ­oxy suffix.
Number shows where the ­ol or c=c are. Di-, Tri-, Tetra-, show the number of groups attached e.g.
methyl group.
Isomers: Same molecular formula, different structural formula.
Octane number: The tendency of a fuel to auto-ignite compared to iso-octane. Auto ignition in
petrol engines causes knocking. Arenes>Cycloalkanes>Alkanes.…read more

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Chemistry Notes
Particulates Incomplete combustion of Irritation in lungs
hydrocarbons in diesel…read more

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