Organic Chemistry

• how is crude oil formed?

  over millions of years from the remains of tiny sea creatures called plankton which were buried in mud
• crude oil is a mixture of hydrocarbons
• what are hydrocarbon molecules?

  only contains carbon and hydrogen
• what is the general formula for alkanes?

  CnH2n+2
• which are saturated? alkanes or alkenes

  alkanes
• which are a single bond? alkane or alkene

  alkane
• first 4 hydrocarbons

  methane, ethane, propane, butane
• what happens to the viscosity as the size of hydrocarbons increase?

  increases
• short chain hydrocarbons are easily flammable but long chain hydrocarbons are not
• as you increase the size of hydrocarbons, the boiling point increases
• properties of short chain hydrocarbons:

  1. highly flammable
  2. low boiling points
  3. lower viscosity
• properties of long chain hydrocarbons:

  1. less flammable
  2. high boiling points
  3. higher viscosity
• what happens during combustion?

  carbon and hydrogen atoms in the fuel react with oxygen. the carbon and hydrogen are oxidised
• what is complete combustion?

  process of burning a fuel with unlimited oxygen, which then produces carbon dioxide and water
• balance this equation? C3H8 + O2 ->CO2+H20


  C3H8 + 5 O2 ->3 CO2+4 H20
• how does fractional distillation work?

  1. crude oil is heated at a high temp= boil
  2. all of the hydrocarbons evaporate and turn into gas
  3. the column is hotter at the bottom and cooler at the top
  4. hydrocarbon vapours rise up the column and condense when they reach their BP
• where are short hydrocarbons removed?

  at the top where its cooler so long chain hydrocarbons are removed from the bottom where it is hotter
• what is fractional distillation used for?

  in the petrochemical industry for solvents lubricants, detergents, polymers
• order of fractional distillation: bottom to top

  1. heavy fuel oil
  2. diesel
  3. kerosene
  4. petrol
  5. petroleum gases
• what is cracking?

  a process where a long chain alkane is broken down to produce smaller and more useful molecules
• what are shorter chain alkanes used for?

  Fuel in cars
• 2 ways of cracking?

  catalytic and steam
• what is catalytic cracking?

  the use of high temp and a catalyst which speeds up the reaction
• what is steam cracking?

  the use of high temp and steam
• alkenes have double covalent bonds and are unsaturated
• which is more reactive alkenes or alkanes?

  alkenes
• test for alkene:

  1. mix bromine water with alkene and shake
  2. it will then turn colourless
• what is the general formula for alkenes?

  CnH2n
• pentene has 5 carbon atoms. work out the molecular formula for pentene and draw the displayed formula?

  C5H10

  
• why are alkenes unsaturated?

  they have 2 fewer hydrogen atoms than the alkane with the same no of carbon atoms
• compare alkanes and alkenes:

  • both are hydrocarbons and contain same carbon atoms
  • both react with oxygen in complete combustion to produce water n co2
  • both react with oxygen in incomplete combustion for water and carbon monoxide and carbon
  • alkenes can react with halogens and polymerise
  • alkenes are more reactive
• what is a functional group?

  part of a molecule that determines how it reacts
• what is a homologous series?

  have the same functional group and similar chemical properties.
• alkenes produce incomplete combustion = alkenes burn in air with smoky flame
• reacting an alkene with hydrogen produces alkane = hydrogenation
• what happens when an alkene reacts with a water?

  hydration= make an alcohol

  the water must be in the form of steam with a high temp of 300 and a pressure of 70 atmospheres

  use phosphoric acid to speed reaction
• what happens when you react an alkene with chlorine?

  forms dichloroethane
• what happens when u react an alkene with bromine?

  dibromoethane
• what happens when you react an alkene with iodine?

  diiodoethane
• uses of alcohol?

  drinks fuels