Thermochemistry/Fuels

• Organic Chemistry


  Study of compounds of carbon
• Hydrocarbon


  Compound containing only hydrogen & carbon
• Fossil Fuels


  Fuels that were formed from the remains of plants & animals that lived millions of years ago
• Homologous Series

  • Series of compounds of similar chemical properties
  • Showing gradations in physical properties
  • Having a general formula for its members
  • Each member having a similar method of preparation
  • Each member differs from the previous member by a CH2 Unit
• Unsaturated Compound


  Contains one or more double or triple bonds between the atoms in the molecule
• Octane Number


  The measure of tendency of a fuel to resist knocking
• Catalytic Cracking


  The breaking down of long-chain hydrocarbon molecules by the action of heat & catalysts into short-chain molecules for which there is a greater demand
• Heat of reaction


  Heat change when the numbers of moles of reactants indicated in the balanced equation for the reaction react completely
• Heat of combustion


  Heat change when one mole of the substance is completely burned in excess oxygen
• Kilogram calorific value


  Heat energy produced when 1 kg of the fuel is completely burned in oxygen
• Bond energy


  Average energy required to break one mole of a particular covalent bond & to separate the neutral atoms completely from each other
• Heat of neutralisation


  Heat change when one mole of H+ ions from an acid reacts with one mole of OH- ions from a base
• Heat of Formation


  Heat change that takes place when one mole of a compound in its standard state is forward from its elements in their standard states
• Hess's Law


  If a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate stages is equal to the heat change is the reaction is carried out in one stage
• Chloroalkane


  Compound in which one or more of the hydrogen atoms in an alkane molecule have been replaced by chlorine atoms
• Functional Group


  An atom/group of atoms which is responsible for the characteristic properties of an organic compound or a series of organic compounds
• Condensation reaction


  Chemical reaction in which two molecules combine to form a larger molecule with the loss of a smaller molecule such as water
• Steam distillation


  Separations process used to isolate compounds at temperatures below their decomposition temperatures. It is carried out by bubbling steam through the material & distilling off the immiscible liquids
• Principle of steam distillation

  A mixture of two immiscible liquids boils at a temperature that is below that of the boiling points of each of the individual liquids. The hot mixture of water vapour (from the steam) and oil (from the plant) is passed through a condenser & the distillate that is collected contains a mixture of water & oil
• Emulsion


  Dispersion of small droplets of one liquid in another liquid in which it is not soluble
• Liquid-Liquid Extraction


  Technique in which two immiscible liquids (eg. oil of cloves & water) are separated using a solvent (eg. cyclohexane) in which one of the components of the mixture (in this case oil of cloves) has a higher solubility than the other (in this case water), i.e. the organic component is removed from the emulsion by dissolving this organic component in an organic solvent