chemistry

• Crude oil is a mixture of different hydrocarbons found in natural underground reservoirs
• Crude oil needs to be refined after being pumped out of the ground
• Crude oil contains hydrocarbons of different sizes, typically with a lot of big molecules
• Fractional distillation is a process used to separate mixtures of substances with different boiling points
• Fractionating columns are used on an industrial scale to separate crude oil into different fractions
• The main fractions obtained through fractional distillation of crude oil are:

  • Refinery gases (C1-C4) used for domestic heating and cooking
  • Gasoline (C5-C10) used as fuel for motor vehicles
  • Naphtha (C8-C12)
  • Kerosene (C8-C12) used as fuel for aircraft
  • Diesel (C14-C20) used as fuel for motor vehicles
  • Lubricants (C20-C50) with high boiling points
  • Fuel oil (C50-C70) used to power large ships
  • Bitumen (>C70) important component of tarmac
• As the number of carbons in the hydrocarbon chain increases:

  • The colors of the fractions become darker
  • The fractions become more viscous
  • The boiling points of the fractions increase
• Crude oil is a mixture of hydrocarbons
• Hydrocarbons are compounds that contain hydrogen and carbon only
• Two hydrocarbons in crude oil are decane and pentane
• The hydrocarbons in crude oil have different properties
• Separation by fractional distillation depends on different boiling points of the hydrocarbons
• Decane has the higher boiling point compared to pentane
• Pentane is more runny than decane
• Pentane catches fire more easily than decane
• Decane burns with a smokier flame compared to pentane
• Decane collects higher up the fractionating column compared to pentane
• Organic reactions can be classified as: substitution, addition, and combustion
• Substitution reactions involve two products
• During substitution reactions, one functional group is replaced by another
• Addition reactions involve combining two or more molecules to form a larger molecule with only one product
• Combustion involves the reaction of a fuel with oxygen, producing water and carbon dioxide
• Cracking is a decomposition reaction that involves the breakdown of one reactant
• Cracking is used to meet the high demand for short chain alkanes by breaking down longer alkanes
• Cracking produces a shorter alkane and an alkene
• There are two types of cracking: thermal cracking at 750°C and 70atm, and catalytic cracking at 500°C using zeolite
• Definition of a fuel: A substance that, when burned, releases heat energy
• Five fuels obtained from crude oil: Petrol, diesel, kerosene, heavy fuel oil, liquefied petroleum gases
• Other uses for products of fractional distillation: Solvents, lubricants, polymers, detergents
• Combustion: The reaction of a fuel with oxygen
• Boiling points and viscosity change with the length of an alkane: The longer the alkane, the higher its boiling point and viscosity because the molecules are larger, leading to more intermolecular forces of attraction
• Fossil fuels: Coal, oil, natural gas, crude oil
• Fossil fuels contain carbon, hydrogen, and small quantities of sulfur
• Components needed for fire: Fuel, oxygen
• Key reaction for combustion: Fuel + Oxygen → Carbon Dioxide + Water
• Complete combustion: Occurs when oxygen is in excess, resulting in the full combustion of fuel
• Incomplete combustion: Occurs when there is not enough oxygen for a complete reaction, leading to the production of unburnt fuel (soot), carbon monoxide, and water
• Toxicity of carbon monoxide: Odourless gas that can cause dizziness, loss of consciousness, and death by binding to haemoglobin, preventing oxygen and carbon dioxide binding
• Formation of sulfur dioxide during combustion of impurities in fuel: Sulfur reacts with oxygen to form sulfur dioxide, which can dissolve to produce sulfuric acid
• Effects of combustion on the environment: Release of carbon dioxide, carbon monoxide, oxides of nitrogen, and sulfur into the atmosphere