Alkanes

• What is the first step in refining crude oil?


  Oil is pre-heated
• What happens to the fractions during fractional distillation?

  They condense at different heights
• How does the temperature change in the fractional distillation column?

  The temperature decreases upwards
• What does the separation of fractions depend on?


  Boiling point
• What determines the boiling point of hydrocarbons?

  Size of molecules
• How do van der Waals forces relate to molecular size?


  Larger molecules have larger van der Waals forces
• What happens to similar molecules during distillation?

  They condense together
• Where do small molecules condense in the column?

  At the top at lower temperatures
• Where do large molecules condense in the column?

  At the bottom at higher temperatures
• What is the nature of the refining process of crude oil?

  • It is a physical process
  • Involves splitting weak van der Waals forces
• What is the purpose of a vacuum distillation unit?

  To distill heavy residues under a vacuum
• How does lowering pressure affect boiling point?

  It lowers the boiling point
• Why is vacuum distillation advantageous?

  It separates heavier fractions without high temperatures
• What is petroleum primarily composed of?

  Alkane hydrocarbons
• What is a petroleum fraction?

  A mixture of hydrocarbons with similar chain length
• What is the boiling point of petrol/gasoline?

  20°C
• What is the boiling point of kerosene (jet fuel)?

  180°C
• What is the purpose of fractional distillation in the laboratory?

  To separate liquids with similar boiling points
• What is the role of the thermometer in fractional distillation?

  It should be at or below the boiling point
• What happens to vapours with higher boiling points during distillation?

  They condense back into the flask
• What is the outcome of complete combustion of alkanes?

  Produces CO2 and H2O
• What is the result of incomplete combustion?

  Produces CO and/or C
• What is the environmental consequence of carbon soot?

  Causes global dimming
• How can SO2 be removed from waste gases?

  By flue gas desulfurisation
• What is the reaction that produces SO2 from sulfur?

  S + O2 → SO2
• What can calcium sulfite be used to make?

  Calcium sulfate for plasterboard
• What is the effect of nitrogen oxides on the environment?

  They form acid rain
• What do catalytic converters remove from exhaust gases?

  CO, NOx, and unburned hydrocarbons
• What is the main greenhouse gas?

  Water vapor
• What is the greenhouse effect mechanism?

  CO2 absorbs infrared radiation
• What is the overall reaction for the formation of chloromethane?

  CH4 + Cl2 → CH3Cl + HCl
• What is a free radical?

  A reactive species with an unpaired electron
• What is the first step in the free radical substitution mechanism?

  Initiation
• What is the essential condition for the initiation step?

  UV light
• What happens during the propagation step?

  Free radicals react with alkanes
• What occurs during the termination step?

  Collision of two free radicals
• What can excess Cl2 promote in substitution reactions?

  Further substitution reactions
• What is the overall reaction for the formation of CCl4?

  CH4 + 4 Cl2 → CCl4 + 4 HCl
• What is the overall reaction for the formation of CFCl3?

  CH3F + 3 Cl2 → CFCl3 + 3 HCl
• What is the importance of placing the free radical dot correctly?

  To indicate the correct carbon in substitution