Developing Fuels

• Volume (dm3) = moles x 24dm3
• $pV =$$nRT$

  p = pressure (Pa)

  v = volume (m3)

  T = temp (K)

  n = moles

  m = mass (g)
• A solid line shows a bond in the plane a dashed line shows a bond into the plane (backwards) a wedged line shows a bond out of the plane (forwards)
• Sigma bonds are single bonds that allow for free rotation
• Pi bonds are found in double bonds which are overlaps of p-orbitals
• Enthalpy change = energy to break bonds + energy to make bonds
• If enthalpy change is negative then it's exothermic if enthalpy change is positive then it's endothermic
• $q =$$mcΔT$

  q = energy change (J)

  m = mass (g)

  c = specific heat capactiy

  ΔT = change in temperature (ºc)
• In an energy level diagram of an endothermic reaction the reactants would have less energy than the products and vice versa for exothermic
• Bond enthalpies are average values representing the energy required to break one mole of the bond in gaseous state
• Enthalpy change of:

  • reaction = substances react completely stand. cond.
  • formation = one mole of a substance is produced from elements stand. cond.
  • combustion = one mole of substance burned completely in oxygen stand. cond.
  • neutralisation = acid and alkali react together to produce one mole of water stand. cond.
  • STANDARD CONDITIONS = 298K, 100kPa, 1.00 moldm-3
• Hess' Law arrows:

  • formation = <-->
  • combustion = -><-
• Catalysts lower the activation energy needed for a reaction by providing an alternative reaction pathway
• Hetrogenous catalysts are in different states to the reactants
• Heterogenous catalysis:

  1. adsorbtion
  2. bonds weakened
  3. bonds made
  4. desorbtion
• Crakcing is the process of converting long-chain hydrocarbons into shorter, more useful hydrocarbons
• Thermal cracking uses high temperatures and pressures
• Catalytic cracking produces aromatic compunds the hydrocarbon vapour is passed over the heated catalyst
• Complete combustion happens when sufficent oxygen is present and fuel is completely burned to form CO2 which contributes to global warming
• Incomplete combustion happens when there isn't sufficient oxygen and carbon monoxide is produced alongisde water
• Carbon monoxide is a toxic gas and is very harmful as it replaces oxygen in the blood
• Oxides of nitrogen and sulfur can also form which can cause photochemical smog and acid rain which can kill wildlife
• Catalytic converters convert harmful products into less harmful ones such as CO2 or H2O
• Boiling points increase as hydrocarbon chain length increases
• Aromatic compounds contain a benzene ring
• Test for alkenes is if bromine water will change from orange-brown to colourless
• Alkenes can undergo electrophilic addition
• Electrophiles are electron acceptors like HBr, Br2 and H2SO4
• Electrophillic addition:

  1. Double bond is broken and a carbocation forms (3 bonds and +ve charge)
  2. Electrophile with negative charge is attracted to the carbocation and forms a bond
• Alkene to alkane needs a Platinum catalyst and room temperature and pressure
• Stereoisomers are the same strucutral formula with different arrangements in space
• E-Z isomerism occurs due to 2 different groups attatched to the carbonds and limited rotation about C=C double bond. E is apart and Z is together (zame zide)
• Cis-Trans isomers form the same as E/Z isomers
• Sustainability is the ability to maintain supply at the rate it's being used like biofuels
• Biofuels like ethanol are fuels that are made from plants that release less harmful products when burned
• Ethanol is a carbon neutral fuel bevause the carbon it gives out when burned is taken in by crops during the growing process. Hydrogen is also carbon neutral as the only product of combustion is water