Cracking Crude Oil & Alkenes

• What is crude oil primarily composed of?

  A mixture of hydrocarbons
• How can different hydrocarbons in crude oil be separated?

  By the length of their carbon chains
• What process is used to separate hydrocarbons in crude oil?

  Fractional distillation
• Which hydrocarbons are the most flammable?

  The shortest hydrocarbons
• What is the characteristic of longer chain hydrocarbons?

  They are thick viscous liquids
• What is the process called that breaks down longer hydrocarbons into shorter ones?

  Cracking
• What type of reaction is cracking?

  A thermal decomposition reaction
• What does thermal decomposition mean?

  Breaking down molecules by heating
• What are the two methods of cracking?

  Catalytic cracking and steam cracking
• What is the first step in the cracking process?

  Heat and vaporize long chain hydrocarbons
• What catalyst is used in catalytic cracking?

  Hot powdered aluminium oxide
• What happens to long hydrocarbons in catalytic cracking?

  They split into smaller hydrocarbons
• What is mixed with hydrocarbons in steam cracking?

  Steam
• What is produced when long chain alkanes are cracked?

  A shorter alkane and an alkene
• What is the balanced equation for cracking decane?

  Decane → Heptane + Propene
• How do you determine the number of carbons in the unknown alkane from decane?

  Subtract known carbons from decane
• What is the formula for the unknown alkane when cracking decane?

  C$_8$H$_{18}$
• What is a homologous series?

  A group of similar compounds
• What is the structural difference between alkenes and alkanes?

  Alkenes have a double bond
• Why are alkenes more reactive than alkanes?

  They have a double bond
• What happens when bromine water is added to alkenes?

  It decolorizes from orange to colorless
• What can alkenes be used to produce?

  Polymers and other chemicals
• What are the key features of alkenes compared to alkanes?

  • Alkenes have a double bond; alkanes have single bonds
  • Alkenes are unsaturated; alkanes are saturated
  • Alkenes are more reactive than alkanes
• What are the steps involved in the cracking process?

  1. Heat and vaporize long chain hydrocarbons
  2. For catalytic cracking, pass vapor over catalyst
  3. For steam cracking, mix vapor with steam and heat
  4. Split long hydrocarbons into shorter ones
• How do you write a balanced equation for cracking reactions?

  1. Identify reactants and products
  2. Count carbons and hydrogens
  3. Ensure the same number on both sides
  4. Adjust for double bonds in alkenes