3.3.2.1 Fractional distillation of crude oil

• What are alkanes?

  Saturated hydrocarbons
• Define petroleum.

  A mixture containing mainly alkane hydrocarbons that can be separated by fractional distillation
• What is crude oil made up of?

  Hydrocarbons
• Example homologous series?

  Alkanes
• Are alkanes saturated or unsaturated?

  Saturated
• Meaning of saturated?

  Molecules that has no double, triple bonds, only single bonds
• Describe the bonding in alkanes?

  Strong non-polar covalent bonds
• What are aliphatic hydrocarbons?

  With branched or unbranched chain of carbons atoms, or rings of carbon atoms that are not aromatic
• Info about alkanes?

  Saturated, has hydrocarbons, not cyclical, no polar bonds, its aliphatic
• Info about cyclo-alkanes?

  Saturated, has hydrocarbons, its cyclical, no polar bonds, and its aliphatic
• Main alkanes properties?

  Polarity, solubility, boiling points
• Alkanes polarity?

  Non-polar as they have similar electronegativity, only has van de waals
• Alkanes solubility?

  Water molecules are too strongly attached to one another by hydrogen bonds to allow non-polar alkanes to slip between them and dissolve, they don't mix with non-polar liquids
• Alkanes boiling-points?

  It increases with chain length, branched chains have lower melting points as chains can not pack as closely together, so weaker VDW
• Why would you expect both alkanes and cycloalkanes to have a similar reaction?

  Both alkanes, C-C bond have the same homologous series, both saturated, only single bonds
• Trend in density as carbon length increases?

  Density increases
• Why do alkanes have such high stabilities?

  Non-polar, fulfilled the octet rule by strongly bonding covalently, no electronegativity
• Alkanes differing properties depend on?

  Length of carbon chain
• Define a mixture?

  Multiple substances not chemically bonded together but exist in a homologous situation
• Define volatility.

  How easy a substance vaporates
• Chain length?

  Hydrocarbons increase in chain length down the fractionating column
• Boiling point?

  Increases down the fractionating column, longer chains, stronger VDW
• Flammability?

  Increases up the fractionating column, more bonds more energy needed
• Viscosity?

  Increases down the group, longer chains, more electrons, more IMF, less likely to flow
• Why is crude oil important?

  Versatile, contains fractions, easier to extract, energy density
• Explain how differing fractions are separated using fractional distillation.

  Heated into a fractionating column, crude oil is vapourised in a furnace, heavy fractions condense near the bottom, lighter fractions condense towards the top as it is cooler, different hydrocarbons enter different heights
• Why are first fractions the easiest to ignite?

  C-H is weaker than C-C so lower activation energy
• Why do higher fractions have a higher viscosity?

  Stronger VDW, more hydrocarbons, more bonds, more energy needed to overcome, more electrons, less likely to flow, long chains, chains packed closely together, less branched