2.5 - Crude oil, fuels and organic chemistry

• What is crude oil?

  • Oil extracted from the earth.
  • Crude oil is a complex mixture of hundreds of hydrocarbons.
  • Hydrocarbons are compounds that contain hydrogen and carbon.
• Carbon chains

  • Carbon can form chains of different lengths.
  • Chains of different lengths have different properties.
• What is this process called?

  Fractional distillation of Crude oil

  
• There are 2 types of hydrocarbons

  • Alkanes
  • Alkenes
• What is the general formula for Alkanes?

  CnH2n+2
• What is the general formula for Alkenes?

  CnH2n
• What is the test for Alkenes?

  • Add bromine water (Br2)
  • Positive test = turns colourless
• What is this the structure of?

  Butane

  
• What is this the structure of?

  Ethene

  
• What would you name this isomer of Butane?

  2-methyle propane

  
• What does this symbolrepresent?

  Reversible reaction

  
• What is the test for alcohol?

  Add acidified potassium diochromate

  Positive = Orange -> Green
• What is the functional group in alcohol?

  O-H
• What is a reversible reaction?


  A reaction that can go in either direction.
• What is equilibrium in terms of a reversible reaction?

  When the reactants are making the products at the same rate as the products are making the reactants
• What is formed during the Haber process?

  Ammonia (NH3)
• What catalyst is used in the haber process?

  Iron catalyst
• Ho do you test for ammonia?

  Ammonia gas turns damp red litmus paper blue
• Combustion of hydrocarbons

  1. Requires oxygen (from the air)

  2. Burning hydrocarbons produces carbon dioxide and water
• Methane + oxygen


  Produces carbon dioxide and water
• All combustion reactions are exothermic, i.e. they release heat
• Hydrogen as a fuel

  • Used as a rocket fuel and in hydrogen fuel cells
  • Produced from water, therefore renewable
  • Water is the only product of its combustion so burning hydrogen does not contribute towards global warming or acid rain
  • Ignites easily
  • Forms an explosive mixture with air
• Ethanol as a fuel

  • Renewable
  • Carbon-neutral, i.e. the amount of carbon dioxide absorbed by plants during photosynthesis balances the amount of carbon dioxide released on burning the fuel made from them
  • Dependent on climate for sugar growth
  • Decreases the amount of land available to grow food crops - could result in higher food prices
• Fire triangle

  Factors required for combustion to occur
• Firefighting and fire prevention

  1. Removing one or more factors from the fire triangle

  2. Carbon dioxide and fire blankets can be used to remove oxygen

  3. Water can be used to remove heat

  4. Trees can be felled to remove fuel in a forest fire
• Hydrocarbons

  • Compounds that contain carbon and hydrogen atoms only
  • Carbon atoms have the ability to form bonds with other carbon atoms resulting in the formation of hydrocarbon chains
  • Longer the chain, the higher the boiling point
• Crude oil

  • Complex mixture of hydrocarbons
  • Produced from the remains of dead marine animals and plants that lived around 300 million years ago
  • Covered by sand and other sediments over time, pressure and heat caused the remains to break down, forming crude oil
• Fractional distillation

  1. Crude oil is boiled/vaporised before it enters the fractionating column

  2. Hydrocarbons condense at different heights in the column

  3. Lower the boiling point, the higher in the column a compound is collected

  4. Fractions are mixtures containing hydrocarbon compounds that have similar chain lengths and, therefore, similar boiling points
• Intermolecular forces

  • Larger molecules have more intermolecular forces, and so more energy is needed to overcome them in order for melting or boiling to occur
  • Longer chain hydrocarbons are more viscous (i.e. thicker liquids, less easy to pour)
• Factors required for combustion

  • HEAT
  • FUEL
  • OXYGEN
• Cracking hydrocarbons

  1. Breaking large hydrocarbons into smaller ones by heating heavier fractions to a high temperature in the presence of a catalyst

  2. An alkene is also formed
• There is greater demand for the smaller hydrocarbons and alkenes, such as ethene, are the starting material for the production of many plastics
• Alcohols

  Contain the functional group —OH, which is responsible for their properties
• Ethanol production by fermentation

  1. Yeast contains an enzyme which breaks down sugar, making ethanol and carbon dioxide

  2. Needs to happen in anaerobic conditions (when deprived of oxygen)

  3. Needs to happen at about 35°C
• Sale of alcoholic drinks


  Generates significant revenue for the government
• Alcohol abuse


  Significant amount of public money spent each year in treating alcohol-related illnesses and in dealing with various other issues
• Monomers


  Small, reactive molecules that can be joined together to make a polymer
• Reactivity of a monomer


  Arises from the presence of its double bond
• Polymerisation


  One of the bonds breaks to allow the molecule to join to another
• Alkanes


  Contain single bonds between the carbon atoms only and are said to be saturated