Alkanes

• What is the chemical formula for methane?

  CH₄
• What is the structural formula for ethane?

  H-C-C-H
• What is the chemical formula for propane?

  C₃H₈
• What is the structural formula for butane?

  H-C-C-C-C-H
• What is the chemical formula for pentane?

  C₅H₁₂
• What is the structural formula for hexane?

  H-C-C-C-C-C-C-H
• What is the general formula for alkanes?

  • CₙH₂ₙ₊₂
• What are alkanes classified as?

  • Saturated hydrocarbons
  • Only have single bonds
• What are cycloalkanes?

  • Ring of carbon atoms
• What is the polarity of alkanes?

  Non-polar
• Why are alkanes considered non-polar?

  Electronegativities of carbon and hydrogen are similar
• What type of forces do alkanes exhibit?

  Weak van der Waals forces
• How does boiling point change with chain length in alkanes?

  Boiling point increases with chain length
• Why do branched alkanes have lower boiling points?

  They can't pack closely together
• Are alkanes soluble in water?

  No, they are insoluble
• Why are alkanes insoluble in water?

  Hydrogen bonds in water are stronger
• What is crude oil formed from?

  • Breakdown of plants and animals
  • Formed millions of years ago
  • High pressures and temperatures deep below Earth's surface
• What does crude oil contain?

  • Mixture of compounds
  • Different lengths
  • Different branching
  • Cyclocompounds
  • Compounds with other elements
• What is the process of fractional distillation of crude oil?

  1. Oil is heated to about 350°C
  2. Enters a column hotter at the bottom
  3. Trays at each level with different temperatures
  4. Liquid fractions are piped off
• What are the fractions obtained from fractional distillation?


  • Refinery gas
  • Petrol (gasoline)
  • Kerosene
  • Naptha
  • Diesel
  • Lubricating oil
  • Fuel oil
  • Bitumen
• What is the boiling point range for gasoline?

  25-60°C
• What is the boiling point range for kerosene?

  180-220°C
• Why is cracking performed on alkanes?

  To meet the demand for shorter chain alkanes
• What are the products of cracking?

  • Branched alkanes
  • Cycloalkanes
  • Alkenes
  • Hydrogen
• What are the types of cracking?

  • Thermal cracking
  • Catalytic cracking
• What are the conditions for thermal cracking?

  High temperatures and high pressure
• What are the advantages of catalytic cracking?

  Less energy and higher yield of products
• What is the function of a catalytic converter?

  • Transforms pollutant gases into harmless gases
• What is produced during complete combustion of alkanes?


  Carbon dioxide and water
• What is produced during incomplete combustion of alkanes?

  Carbon monoxide and water
• What are the pollutant gases from combustion?

  • Carbon dioxide
  • Carbon monoxide
  • Nitrogen oxides
  • Sulfur oxides
  • Carbon particulates
• What is global warming caused by?

  • Increase in greenhouse gases
  • Absorb and emit infrared energy
• What is sulfur contamination in fossil fuels?

  • Found as an impurity in crude oil
  • Burns to produce SO₂
• What is acid rain formed from?

  SO₂ and SO₃ dissolving in water
• How can sulfur oxides be removed from fuels?

  • Remove sulfur impurities before burning
  • Use a base like CaO after burning
• What are the characteristics of alkanes?

  • Saturated hydrocarbons with single bonds
• What happens to the boiling point of alkanes as the chain length increases?

  It increases due to more van der Waals forces
• What is the role of zeolite in catalytic cracking?

  It acts as a catalyst to lower energy costs
• What is the environmental impact of thermal cracking?

  High energy costs and environmental impact
• What is the significance of branched alkanes in fuels?

  They increase the octane number of fuels