Organic chemistry

  • Created by: holly6901
  • Created on: 10-06-19 18:45

Crude oil

  • Hydrocarbons are molecules made up of only hydrogen and carbon atoms.
  • Hydrocarbons differ in their size, which can change the properties of the hydrocarbon.
  • Crude oil is a mixture of lots of different compounds that are not chemically combined.
  • Most of the compounds in crude oil are hydrocarbons.
  • Crude oil is found in rocks and is used to produce fuels and other important chemicals.
  • Crude oil is formed from the fossilised remains of ancient plankton
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Alkanes

  • In alkanes, carbon atoms bond to four other atoms (hydrogen or carbon).
  • We call them saturated hydrocarbons as they only contain single bonds with other atoms.
  • Alkanes are quite unreactive but can burn well.
  • This makes them useful fuels.
  • The general formula for alkanes is CnH(2n+2).
    • E.g. if a hydrocarbon contained 7 carbon atoms, the number of hydrogen atoms would be (2 x 7) + 2 = 16.
    • Therefore, the formula for this hydrocarbon would be C7H16.
  • The 4 smallest alkanes, in ascending size order, are:
    • Methane (CH4).
    • Ethane (C2H6).
    • Propane (C3H8).
    • Butane (C4H10)
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Properties of hydrocarbons

  • Hydrocarbons with longer chains have higher boiling points.
  • Hydrocarbons with longer chains have higher viscosity (i.e. they are thicker and flow less easily).
  • Hydrocarbons with longer chains are less flammable.
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Fractional distillation

  • Hydrocarbons with few carbon atoms are called 'short-chain hydrocarbons'.
  • Hydrocarbons with lots of carbon atoms are called ‘long-chain hydrocarbons’.
  • Crude oil is heated until it evaporates.
  • Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
  • The temperature is highest at the bottom of the column. Long-chain hydrocarbons condense at the bottom and are collected as liquids.
  • Short-chain hydrocarbons have lower boiling points. They pass up the column and condense at lower temperatures nearer the top.
  • The fractions are collected. They are then processed to create end products:
    • Fuels (e.g. petrol, diesel) are a common end product.
    • The petrochemical industry can use some fractions as feedstock (material used in an industrial process) to make solvents, lubricants, detergents etc.
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Processes of fractional distillation

  • Crude oil is heated until it evaporates.
  • Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
  • The temperature is highest at the bottom of the column. Long-chain hydrocarbons condense at the bottom and are collected as liquids.
  • Short-chain hydrocarbons have lower boiling points. They pass up the column and condense at lower temperatures nearer the top.
  • The fractions are collected. They are then processed to create end products:
    • Fuels (e.g. petrol, diesel) are a common end product.
    • The petrochemical industry can use some fractions as feedstock (material used in an industrial process) to make solvents, lubricants, detergents etc.
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Burning hydrocarbons

  • If alkanes are burned without enough oxygen, then carbon monoxide can be created:
    • 2C + O2 → 2CO.
  • Carbon monoxide is a colourless, odourless, toxic gas.
  • The combustion (burning) of hydrocarbons when there is a good air supply involve:
    • Energy release.
    • The oxidation of carbon and hydrogen to create carbon dioxide and water.
    • The combustion (burning) of hydrocarbons when there is a good air supply involve:
      • Energy release.
      • The oxidation of carbon and hydrogen to create carbon dioxide and water.
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Cracking

  • Vapourised heavy hydrocarbons are mixed with steam in a high temperature environment.
  • The products include alkanes and alkenes.
    • E.g. decane → octane + ethene
  • Vapourised heavy hydrocarbons are passed over a hot catalyst.
  • The products include alkanes and alkenes.
    • E.g. hexane → butane + ethene
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Formulations

 

  • In a formulation, each component helps to decide what the mixture’s overall properties are.
  • To ensure that a formulation does what it is supposed to, each chemical component must be present in a precisely measured quantity.
  • Formulations are everywhere.
  • Examples include cleaning agents, fuels, metal alloys, fertilisers and medicines.

 

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