alkenes and cracking

• What is crude oil primarily composed of?

  A mixture of different hydrocarbons
• What process is used to separate hydrocarbons by carbon chain length?

  Fractional distillation
• Which hydrocarbons are the most flammable?

  The shortest hydrocarbons
• What is the main 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 formula for decane?

  C₁₀H₂₂
• What is the balanced equation for cracking decane into ethene?

  C₁₀H₂₂ → C₈H₁₈ + C₂H₄
• What is the structural difference between alkenes and alkanes?

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

  Due to the presence of 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 cracking long chain hydrocarbons?

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

  1. Identify reactants and products
  2. Count carbon and hydrogen atoms
  3. Adjust coefficients to balance both sides
  4. Ensure products include an alkene and a shorter alkane