ALKANES + ALKENES

• formula for alkanes?

  CnH2n+2
• whats the trend in boiling points for alkanes?

  Increase as they get more carbons in their chain so stronger van der waals between molecules
• what are the products of complete combustion?

  carbon dioxide and water
• what are the products of incomplete combustion?

  Carbon monoxide, soot, and water
• where are alkanes found?

  CRUDE OIL WHICH IS A MIXTURE OF DIFFERENT LENTGH HYDROCARBONS
• how does fracional distillation work?

  vapourised oils enter the column, long hydrocarbons condense at the bottom short chain rise to the top.

  the column acts as a temperature gradient due to the different chain lengths
• what is cracking?

  breaking long chain alkanes into shorter ones
• what is thermal cracking?

  • high temperature of about 700k
  • high pressure of 70 atm
  • products are mainly alkenes
• what is catalystic cracking?

  450 c

  zeolite catalyst

  low pressure

  produce aromatic hydrocarbons useful for fuels in cars
• why is a zeolite catalyst good?

  lowers the temperature and pressure needed which lowers the cost but speeds up the proceess
• what is the greenhouse effect?

  co2 absorbs infared from the sun and emits some of it back to the earth, warming the they can do this as they have polar bonds
• what are oxides of nitrogen?

  nitrogen and oxygen from the air combine under high pressure and temperature in car engines to break the triple N bond
• why are oxides of nitrogen bad?

  Pollution
• what are catalytic converters?

  help reduce the amount of unburnt hydrocarbons and oxides of nitrogen from going into the atmosphere
• what is the equation for catalytic converters?

  2NO + 2CO --> N2 + 2CO2
• what is acid rain?

  some fossil fuels have sulphur based impurities and when they burn they react with oxygen to form sulfur dioxide which is an acidic g as and reacts with water to form sulphuric acid which falls as acid rain. acid rain damages plants kills fish and erodes buildings
• what is the hydration of alkenes?

  makes ethanol

  phosphoric acid catalyst
• what is fermentation?

  renewable as it uses glucose

  yeast in anaeroic conditions

  exothermic

  c6h12o6 --> 2C2H5OH + 2CO2

  yeast acts as an enzyme

  however you have to use fractional distillation after to obtain pure ethanol

  slow

  not a big yield
• what are biofuels?

  Renewable fuels made from organic matter, such as plants or animal waste.
• what are the advantages of biofuels?

  biofuels are renewable so sustainable

  theyre carbon neutral

  THEY DO make carbon dioxide but the carbon dioxide is abosrbed by the sugar cane as its growing
• are biofuels carbon neutral?

  nearly

  when ethanol is burnt, carbon dioxide is produced however it is used by plants in photosynthesis

  when you ferment glucose , 2 moles of carbon dioxide is made and when you burn ethanol, 4 moles of carbon dioxide are made so in total you have 6 moles which get absorbed by the plants so it cancels out

  6CO2 + 6H20 --> C6H12o6 +6O2
• What reagent and condition is needed for alkene to alchohol?


  aqueous phosphoric acid

  300 degrees

  highovressure
• Why is a temperature of 35 Used?

  too low is too slow amd too high denatured the enzymes
• What are the advantages of using glucose to make ethanol?


  theyre renewable and are carbon neutral as it absorbs the carbon dioxide released by burning ethanol and fermentation
• What’s the equation for th complete comnustiom of ethanol?

  2C2H5OH + 6O2 —> 4CO2 + 6H20
• what are some economic and ethical problems with using ethanol as a biofuel?

  economic - petrol car engines have to be modified to use fuels with ethanol

  ethical - when using land to grow crops foe ethanol, the land cant be used to make food
• why cna CO2 emit UV light back to the earth?

  it has polar bonds
• how do you remove sulphur based impurities?

  wet scrubbing by using calcium oxide or calcium carbonate with water
• what is the equation for wet scrubbing with calcium oxide?

  CaO + 2h20 + SO2 --> CaSo3 + 2H20
• what is the eqution for wet scrubbing with calcium carbonate?

  CaCO3 + SO2 + 2h2O --> CaSO3 + 2H2O +CO2
• how does wet scrubbing work?

  when mixing the calcium oxide or calcium carbonate with water , an alkaline slurry is made which is then sprayed onto the gasses. the sulphur dioxide will react with the slurry.
• what type of alkane would be liquified more easily?


  the one with the longer carbon chain due to its higher boiling point