cracking and alkenes

• What is crude oil primarily composed of?

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

  Fractional distillation
• Why are shorter hydrocarbons considered better fuels?

  They are more flammable
• What happens to longer chain hydrocarbons during cracking?

  They are broken down into shorter hydrocarbons
• What type of reaction is cracking?

  Thermal decomposition reaction
• What does "thermal" refer to in thermal decomposition?

  Heating
• What does "decomposition" mean in thermal decomposition?

  Breaking down molecules
• 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 smaller hydrocarbons
• What is mixed with hydrocarbons in steam cracking?

  Steam
• What is produced alongside shorter hydrocarbons during cracking?

  Alkenes
• How do you write a balanced equation for cracking?

  Ensure carbons and hydrogens are equal
• What is the formula for decane?

  C₁₀H₂₂
• What is the formula for ethene?

  C₂H₄
• What is the unknown alkane produced when decane is cracked into ethene?

  C₈H₁₈
• What distinguishes alkenes from 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 and alkanes?

  • Alkenes:
  • Have a double bond
  • More reactive than alkanes
  • Unsaturated
  • Alkanes:
  • Have only single bonds
  • Less reactive
  • Saturated
• What are the steps involved in cracking long chain hydrocarbons?

  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 balance a chemical equation for cracking?

  1. Write the reactants and products
  2. Count carbons and hydrogens
  3. Adjust coefficients to equalize both sides
  4. Ensure all products are accounted for