Alkanes

• What is crude oil?

  Crude oil is a naturally occurring, unrefined petroleum product that is composed of hydrocarbon deposits and other organic materials.
• How is crude oil separated into fractions?


  Fractional distillation where the fractions are boiled and then condensed at their fraction and collected
• How do you carry out fractional distillation?

  1. the fractionating column has a temperature gradient
  2. the crude oil is heated until vaporised and enters the column
  3. hydrocarbons with very high boiling points immediately condense into higher temperatures
  4. smaller chain hydrocarbons are collected at the top of the column.
• Why are Alkenes cracked?

  To produce smaller, more useful hydrocarbons.
• What are the two types of cracking?

  1. thermal cracking
  2. catalytic cracking
• What is the process of thermal cracking?

  requires high temps (1000$^{\circ}$C) ands high pressure (up to 70 atm)
• What is the process of catalytic cracking?

  Usee a lower temperature (450$^{\circ}$C) ands high pressure slight pressure in the presence of a zeolite catalyst
• What does thermal cracking produce?

  Shorter hydrocarbon molecules and unsaturated hydrocarbons.
• What does catalytic cracking produce?

  mainly aromatic hydrocarbons
• What type of reaction is cracking?

  endothermic
• What is complete combustion?

  When products are burnt in excess of oxygen
• What are the products of complete combustion?

  carbon dioxide and water
• What is incomplete combustion?

  When a substance is burnt in a limited supply of oxygen.
• What are the products of incomplete combustion?

  carbon monoxide and water
• What do car exhaust fumes produce?

  carbon monoxide

  nitrogen oxides
• Why is carbon monoxide dangerous?

  the CO binds to haemoglobin preventing it from binding with oxygen so organs have less of an oxygen supply.
• Why are nitrogen oxides hazardous?

  they can cause smog and acid rain
• What is the role of a catalytic converter?

  Reduce hazardous pollutants
• What are some of the features of a catalytic converter?

  precious metals are coated in a honeycomb to increase surface area so the reaction can be carried out quickly, this also reduces the amount of metal used so the costs are reduced
• What is the reaction for the oxidation of CO to CO2?

  2CO + O2 → 2CO2
• What is produced when CO is oxidized with O2?

  Carbon dioxide (CO2)
• How can CO be oxidized in the presence of NO?

  2CO + 2NO → 2CO2 + N2
• What is the reaction for the reduction of NO to N2?

  2CO + 2NO → 2CO2 + N2
• What is the product of reducing NO in the presence of CO?

  Nitrogen gas (N2)
• How do the reactions for oxidation and reduction of CO and NO relate to each other?

  Both involve CO and produce CO2 and N2
• What is the reactivity of alkanes?

  Alkanes are generally unreactive due to the presence of strong carbon-carbon and carbon-hydrogen bonds.
• how are free radicals formed?

  • every covalent bond is a shared pair of electrons
  • if each atoms takes 1 of these electrons, 2 free radicals are formed
  • this is called a homolytic bond fission
  • they are represented by a dot next to the chemical name of the element
• properties of free radicals?

  they are very reactive
• How can methane and chlorine react?

  They react via a free radical substitution reaction
• What are the stages of free radical substitution?

  Initiation, propagation and termination
• What is a free radical?

  An atom or molecule with an unpaired electron.