Cracking

• What is meant by cracking in the context of hydrocarbons?

  Cracking is the process of breaking down long chain alkanes into shorter, more useful molecules.
• What is the general formula for alkanes?

  The general formula for alkanes is $C_nH_{2n+2}.$
• Why are long chain hydrocarbons not good fuels?

  Because they are not very flammable.
• What is the purpose of cracking in hydrocarbon processing?

  • Convert long chain hydrocarbons into shorter chain hydrocarbons
  • Produce more useful molecules for fuels
• What are the two methods of carrying out cracking?

  The two methods are catalytic cracking and steam cracking.
• What conditions are used in catalytic cracking?

  High temperature and a catalyst are used in catalytic cracking.
• What conditions are used in steam cracking?

  High temperature and steam are used in steam cracking.
• What is an alkene?

  An alkene is a hydrocarbon that contains a double covalent bond between two carbon atoms.
• Why are alkenes considered more reactive than alkanes?

  Because they contain a double covalent bond.
• What is the test for alkenes using bromine water?

  • Shake the alkene with bromine water
  • Bromine water turns colorless
• What happens to bromine water when it reacts with an alkene?

  Bromine water turns colorless when it reacts with an alkene.
• Why is it important to say that bromine water turns colorless and not clear?

  Because "colorless" accurately describes the reaction.
• How do you balance a chemical equation for cracking?

  • Ensure the number of carbon and hydrogen atoms is the same on both sides
  • Adjust coefficients as necessary
• What must be true about the number of carbon and hydrogen atoms in a balanced cracking equation?

  They must be the same on both sides of the equation.
• If a cracking reaction has 25 carbon atoms and 52 hydrogen atoms on the left, how many carbon atoms are in the second product if the right side has 20 carbon atoms?

  5 carbon atoms are in the second product.
• If a cracking reaction has 40 carbon atoms and 82 hydrogen atoms on the left, how many hydrogen atoms are in the first product if the right side has 14 hydrogen atoms?

  68 hydrogen atoms are in the first product.