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 purpose of cracking in hydrocarbons?

  To break down long hydrocarbons into shorter ones
• 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 both catalytic and steam cracking?

  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 two 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 + Ethene
• How do you determine the unknown alkane in the cracking of decane?

  Subtract carbons and hydrogens of products
• 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 with similar properties
• What is the structural difference between alkenes and alkanes?

  Alkenes have a double bond, alkanes do not
• Why are alkenes more reactive than alkanes?

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

  It decolorizes from orange to colorless
• What is the test for alkenes?

  Decolorizing bromine water
• How can alkenes be used in polymer production?

  Double bonds can break to form new bonds
• What are the key features of alkenes compared to alkanes?

  • Alkenes have double bonds; 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 number of each is equal on both sides
  4. Adjust products as necessary