hydrocarbons

• Explain how ethene is produced in the cracking process

  1. when decane is heated it vaporises
  2. decane vapour breaks down when it comes in contact with hot porous pot(catalyst)
  3. Large molecules of decane produce smaller molecules including ethene

  
• General formula


  A formula that shows the relationship between the number of hydrogen atoms within a molecule

  e.g. for alkanes - CnH2n+2
• How is sulfur dioxide formed?

  Many fossil fuels (hydrocarbons) contain sulfur impurities

  When these fuels are burnt sulfur is oxidised to form sulfur dioxide
• Why would a suck-back happen in catalyst experiment and why might this be dangerous?

  To balance out the pressure, water would travel back up the delivery tube into the test tube.

  When the cold water touches the hot water in the test tube, it could cause it to smash or explode
• features of a homologous series

  -same general formula (2n+2)

  -have same functional group

  -have similar chemical properties

  -There is a graduation (gradual change) in physical properties

  -Each member differs by CH2
• What is common impurity in hydrocarbon fuels?

  Sulfur -could cause acid rain
• order of alkanes:

  • methane
  • ethane
  • propane
  • butane
  • pentane
  • hexane
• all the possible products of combustion

  • carbon / soot
  • carbon monoxide
  • carbon dioxide
  • water
• bitumen use


  surface of roads and roofs (waterproofing)
• refinery gases use

  domestic heating and cooking
• sulfuric acid 


  H2SO4
• Name order of fractions

  • refinery gases
  • gasoline
  • kerosine
  • diesel
  • fuel oil
  • bitumen
• What is the average percentage of oxygen in the air?

  21%
• smallest isomer of alkene

  butene
• What is the average percentage of CO2 in the air?


  0.04%
• Effects of acid rain

  -damages plants

  -kills fish

  -damages stonework
• Two pollutant gases that form acid rain

  sulfur dioxide

  nitrogen oxide
• How does sulfur dioxide cause acid rain?

  When sulfur dioxide reacts with water and air it forms sulfuric acid
• How can alkenes be separated?

  Fractional distillation
• kerosine uses

  aircraft fuel
• gasoline uses?


  car fuel
• possible products for an incomplete combustion

  -carbon/soot

  -carbon monoxide
• what are hydrocarbons?


  a compound made up of hydrogen and carbon ONLY
• condition needed to react an alkane with bromine

  UV light
• what is meant by the term fraction?

  hydrocarbons with similar boiling points
• why does incomplete combustion occur?

  insufficient oxygen
• Why is it important to remove the compound C6H12S from a fuel?

  -Forms sulfur dioxide

  -causes environmental problems such as acid rain which damages trees
• What is an impurity?

  An unwanted substance found mixed into a useful substance
• During cracking how do you prevent the water from rising up the delivery tube?

  remove the delivery tube from water before stopping heating
• solid product of incomplete combustion


  carbon/soot
• Which fraction is most viscous?

  bitumen
• How does fractional distillation separate crude oil?

  -Crude oil mixture heated up until it becomes vaporised

  -The vaporised crude oil is pumped into fraction column

  -Vapour rises through column which is hotter at bottom and gets cooler further up

  -Different hydrocarbons rise until the temp falls below their boiling point where they condense and are collected in the trays

  -To prevent the liquid running back down the column, on each layer there are bubble caps
• What is crude oil?

  a mixture of hydrocarbons
• Name two pollutant gases that form acid rain when dissolved in water

  -sulfur dioxide -> sulfurous acid

  -nitrogen dioxide -> nitric acid
• What will you see in the tests when propane and propene reacted with bromine water?

  bromine water is orange (1)

  propane = bromine water remains orange (2)

  propene = bromine water decolourises
• smallest alkene


  ethene
• state one feature of propane molecule which is not shown from molecular formula

  its bonds
• cracking


  longer hydrocarbons broken into shorter hydrocarbons
• what is meant by an unsaturated hydrocarbon?

  -Contains double bonds

  -Contains hydrogen and carbon only
• Conditions for cracking


  -600-700*C

  -Silica(catalyst)