Developing fuels

• exothermic reaction


  a reaction that gives out energy (and surrounding heat up)
• endothermic reaction


  a reaction that takes in energy (and cools the surroundings)
• E = mc^2


  direct relationship between the energy transferred and the temp change
• enthalpy change


  the heat energy change per more of substance
• standard conditions


  - specific temperature 295K

  - pressure of one atmosphere

  - concentration of 1 mol dm^3
• standard enthalpy change of combustion

  this is the enthalpy change that occurs when one mole of substance is burned completely in oxygen, under standard conditions.
• standard enthalpy change of formation

  The enthalpy change that takes place when one mole of a compound is formed from its elements, with both the compound and the elements being in there standard conditions.
• standard enthalpy change of nutirlisiation

  the enthalpy change when one mole of hydrogen ions reacts with one mole of hydroxide ions to form one mole of water under standard conditions.
• standard enthalpy change of reduction

  the enthalpy change when one more quantities of reactants as stated in an equation react together under standard conditions.
• Enthalpy


  the heat energy transferred per mole substance at constant pressure.
• how to work out enthalpy

  1) E=MCT

  2) convert to KJ

  3) moles of fuel

  4) enthalpy
• E = mc△T


  e= energy transferred (j)

  m= mass of surroundings in grams

  c= specific heat capacity

  △T = change in temperature of surroundings
• limitations - change of combustion of fuels

  loss of energy to the surroundings

  loss of energy to the calorimeter

  incomplete combustions

  evaporation of fuel from the wick
• enthalpy cycle of combustion

  
• Enthalpy cycle of formation

  
• enthalpy change of reaction

  1) E= mc△t

  2) J --> KJ

  3) enthalpy = energy / moles
• uncertainty


  balance = +/- 0.005

  pippet = +/- 0.06

  volumetric flasks = +/- o.2

  burette = +/- 0.05

  measuring cylinder = +/- 0.5

  thermometer = +/- 0.5
• persenage uncertainty


  % = (uncertainty of apparatus / reading of apparatus) x100
• average bond enthalpy


  the energy needed to break one mole of bonds to give separate atoms all in the gaseous state.
• limitations of ABE


  quoted bond enthalpy are averages the same bond in a differing molecule will have slightly different bond enthalpy

  bond enthalpy's are always worked out for compounds in the gaseous state bond enthalpy's will be slightly different if the substance is a liquid or a gas.
• heterogeneous catalyst


  is when the catalyst and the reactant are in different physical states.
• catalyst


  provide alternate reaction parthways with lower activation enthalpy
• Cracking


  alkane = smaller alkane + alkene

  alkane = smaller alkane + cycloalkane
• catalystic cracking


  heating larger hydrocarbons in the presence of a catalyst.
• Catalyst poison


  some molecules absorb more strongly to the surface of a catalyst and block the active sites on the surface.
• testing for alkenes


  bromine water is orange

  BW stays orange with saturated molecules

  BW goes colourless with unsaturated molecules
• addition reactions


  two smaller molecules react to form one large molecule
• modle of heterogeneous catalysis

  1) reactants adsorb onto surface of catalyst

  2) bonds within the reactants weaken and break

  3) new bonds within the products form

  4) the products desorb from the surface of the catalyst
• organic molecules


  the atoms are held together by strong covalent bonds.

  the majority of these are single bonds which are know as sigma bonds a double bond consist of one (σ) sigma bond and one (π) pi bond
• electrophilic


  a positive ion or molecule with a partial positive charge that will be attracted to a negatively charged region and react by accepting a pair of electrons to form a covalent bond.
• Electrophilic addition


  the mechanism via a carbocation intermediate is conformed by the adding of other anions with the electrophile.

  
• addition polymerisation


  the possesses of join together of many smaller monomers to make a long chain polymer.

  no atoms are last only is monomer is unsaturated.
• molar volume


  the volume occupied by one mole of any gas at a certain temperature and pressure.

  volume of one mole of any gas at 298k + 1 atom pre is always 24.0 dm^3
• Avogadro's law of gases


  if temp and pressure stays the same, the same volume of different gases contains equal number of molecules.
• PV=nRT


  p=pressure

  v=volume (m^3)

  n=moles

  r=gas constant

  t=temperature (K)
• isomers


  iso = Greek for the same

  two molecules that have: the same molecular formula but differ in the way their atoms are arranged.
• structural isomers


  Have the same molecular formula but different structural formula.

  three types:

  - chain isomerism

  - position isomerism

  - functional group isomers
• stereoisomers


  - have the same molecular formula

  - have atoms bonded together in the same order.

  - arrangement of atoms in space is different with each isomer.
• E/Z isomerism


  -A type of stereoisomerism

  - they form when there is a lack of free rotation around the c=c bond and there are two different groups on each carbon atom.
• alternative fule to petrol

  - diesel

  - liquid petroleum gas (LPG)

  - ethanol (biofuel)

  - hydrogen