# Developing Fuels - Complete Mindmap

• Created by: Oliver_C
• Created on: 20-05-19 16:40
• Developing Fuels
• Enthalpy Change
• Hess' Law- the total enthalpy change is independent of the route taken
• H(formation):when 1 mole of a compound is formed from its constituent elements.
• H(reaction): the enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation
• H(combustion: enthalpy change when 1 mole of a substance is burnt fully in oxygen.
• Can be calculated using average bond enthalpies
• Enthalpy Change of a Reaction is the total energy absorbed to break bonds minus the energy released in making bonds.
• Why aren't they exact?
• It's just an average of bond enthalpies from different molecules.
• The energy needed to break 1 moles of bonds in the gas state, averaged over many different compounds.
• Bond Enthalpy
• In covalent molecules the positive nucleus is attracted to the shared electrons.
• But this means also the nuclei and electrons also repel
• Bond length is the distance between the nuclei - where the attractive and repulsive forces balance
• The stronger the attraction between atoms the smaller the bond length and the higher the bond enthalpy
• Enthalpy Level Diagrams
• Endothermic
• Activation energy is big, ?H is positive. Reactants have less energy than the products.
• Exothermic
• Reactants has a higher  enthalpy than the products.
• Calorimetry
• Burn fuel using spirit burner for ?H  combustion
• q=mc(delta)T
• Ideally, all heat given out by the fuel will be absorbed by the water, in practice, however, it's not always the case.
• Ideal Gas Equation
• pv=nrT
• p = pressure in Pa
• v = volume in m^3
• n = no. of moles
• r = 8.314
• T = temp. in Kelvin (Celius + 273)
• cm^3 to m^3 divide by 1,000,000
• dm^3 to m^ divide by 1,000
• moles = vol/24 at rtp (298 K & 100kPa)
• Catalysis
• increases the rate of a reaction by providing an alternate reaction pathway with a lower activation energy
• catalyst is chemically unchanged at the end
• e.g. iron in the Haber process
• e.g. need to be used in cracking to reduce the expenses of high temp./pr.
• Heterogeneous Catalysts
• The catalyst is in a different state to the reactants
• Reactions on heterogeneous catalysts
• Reactant molecules are adsorbed onto the surface of the catalyst.
• bonds between the molecule are broken and radicals form
• these radicals react together to make a new molecule
• this new molecule is detached from the catalyst surface
• Poisoning
• Poison clings more strongly to the surface and so stops the reactant from adsorbing
• so the catalyst isn't able to be involved in the reaction it's supposed to be speeding up
• Homogeneous Catalysts are when the catalyst and the reactants are in the same state
• Organic Groups
• aromatic compounds (arenes)
• has a benzene ring
• aliphatic compounds
• alcohols
• alkanes/ alkenes
• carboxylic acids
• ketones
• aldehydes
• esters
• ethers
• Sigma and Pi Bonds
• Sigma
• happens when 2 orbitals overlap, in a straight line, between the two atoms
• This gives maximum electron density between the positive nuclei so sigma bonds are usually very strong
• single covalent bond
• Pi
• weaker than a sigma bond
• when two p orbitals overlap sideways
• the two outer parts of a double covalent bond
• a double bond is made using one pi and one sigma bond
• Isomerism
• Structural Isomers
• Different Carbon Skeleton
• you can branch straight chained molecules
• Functional Groups
• in a different place - e.g. attached to a different carbon
• same atoms can be arranged into different functional groups
• Stereoisomer
• nothing can rotate about the double bond due to the pi bond - they're quite rigid. restricted rotation causes the stereoisomer
• E/Z Isomers
• E/Z - E= hydrogens are on different sides. Z= hydrogens are on same side
• remember only use E/Z when you have 2 hydrogens!
• same shortened structural formula but different arrangement in space
• use cis- or trans- when talking about molecules on either ends of a double bond rather than E and Z
• Addition Reactions of Alkenes
• monomer into a polymer
• repeating units should include brackets, line that extend out of the brackets, a single C-C bond and should have an 'n' on the outside
• Bromine Water to test for C=C bonds
• orange to colourless due to the electrophilic addition of bromine (or bromination) of the unsaturated molecule.
• C-C bonds are saturated and thus doesn't react with the bromine
• Hydrogenation
• Addition of hydrogen to an unsaturated molecule to make an alkane.
• nickel catalyst and 150 degrees celcius
• when the double bond opens up and more atoms can bond with its carbons
• nucleus is attacked by electrophiles
• carbocation
• curly arrow shows the movement of electrons from a place of high electron conc.
• Reacting with water and sulphuric acid to make an alcohol
• sulphuric acid is the catalyst
• you first add the cold sulphuric acid then add water and warm to hydrolyse it.
• Steam Hydration of Ethene
• ethene can be hydrated by steam at 300 degrees Celsius and 60 atm of pressure.
• requires a phosphoric (V) acid catalyst
• reversible and the initial reaction yield is low
• Fuels (i.e. "Wishy-washy Chemistry")
• Carbon Dioxide
• Produced by most burning of fuels
• greenhouse gas, which leads to a greater greenhouse effect, hence more global warming
• generally produced by fossil fuel burning
• Carbon Monoxide
• Incomplete combustion of hydrocarbons
• Poisonous
• binds to haemoglobin and suffocates you
• NOx and Unburnt Hydrocarbons
• reacts with sunlight in the troposphere to form ozone which causes photochemical smog - dangerous for breathing
• Sulphur Dioxide
• acid rain
• can destroy vegetation and limestone builds
• Particulates
• can settle in lungs and cause breathing problems
• Enthalpy change is the heat energy transferred in a reaction at a constant pressure.
• Reactions can be endo- or exothermic.
• Exothermic reactions give out energy, so enthalpy change (?H) is negative.
• E.g. oxidation usually & combustion
• Endothermic reactions take in more energy than is given out, so ?H is +ive
• E.g. thermal decomposition and photosynthesis
• Remember BEN MEX!!
• Standard Conditions
• 298 K and 100kPa, or 1atm
• Elements are in their standard states