CHEMESTRY ⚗

• Alkanes are saturated hydrocarbons
• Alkanes consist of single carbon-carbon bonds and single carbon-hydrogen bonds only
• General formula for an alkane is CnH2n+2, except for alkanes in a ring structure where it is CnH2n
• Methane (CH4) has an H-C-H bond angle of 109.5 degrees
• Different formulas used to present the structure of an alkane: molecular formula, displayed formula, structural formula, skeletal formula
• Naming alkanes is based on the number of carbon atoms in the compound
• Alkanes can exhibit chain isomerism, a type of structural isomerism where the hydrocarbon chain is arranged differently
• Naming branched alkanes involves identifying the longest continuous chain of carbons and additional groups attached to it
• Alkanes do not dissolve in water due to being non-polar
• Crude oil is a fossil fuel made from the breakdown of organic matter, described as non-renewable
• Burning fossil fuels like crude oil releases carbon dioxide and other pollutants like sulphur dioxide
• Fractional distillation is used to separate different molecules of crude oil for various uses
• Industrial cracking breaks longer hydrocarbons into shorter alkanes and alkenes
• Thermal cracking conditions: Temp: 700-1200K, Pressure: 7000kPa, results in a high proportion of alkenes
• Catalytic cracking conditions: Temp: <720K, Pressure: >1atm, uses zeolite catalyst, products are a mixture of alkanes and alkenes mainly used in motor fuels
• Products obtained from catalytic cracking are separated by fractional distillation and decolourise bromine water
• Alkanes are generally very unreactive and won't react with acids, bases, oxidising agents or reducing agents
• Alkanes are very flammable and will react with halogens in the right conditions
• Equation for the complete combustion of methane:

  CH4(g) + 2O2(g) → CO2(g) + H2O(l) ΔH = -890 kJmol-1
• Hydrocarbons are used as fuels because they release a lot of heat on combustion
• Burning fossil fuels pollutes the environment
• Incomplete combustion of hydrocarbons can lead to the formation of carbon monoxide, carbon particulates, and other pollutants
• Pollutants produced during combustion of hydrocarbons include carbon monoxide, nitrous oxides, sulphur dioxide, carbon particulates, unburnt hydrocarbons, carbon dioxide, and water vapour
• Ways to reduce pollutants:

  • Sulphur dioxide can react with oxygen to form sulphur dioxide, which can be removed by reacting with calcium carbonate or calcium oxide
  • Vehicles are fitted with catalytic converters to reduce nitrous oxide and carbon monoxide emissions
• Global warming is caused by the greenhouse effect, where gases trap energy from the sun in the atmosphere
• The greenhouse effect is important for keeping the planet warm enough for life to survive, but human production of carbon dioxide is causing the earth to get warmer
• Zeolite catalyst


  A type of catalyst commonly used in catalytic cracking due to its high surface area and tunable pore size
• Iron catalyst


  Not typically used in catalytic cracking; more commonly used in reactions that involve breaking strong chemical bonds
• Silver catalyst


  Not typically used in catalytic cracking; more commonly used in oxidation reactions
• Copper catalyst


  Not typically used in catalytic cracking; more commonly used in reactions that involve the transfer of electrons
• Iron catalysts


  Facilitate the breaking of strong chemical bonds, such as in the production of ammonia from nitrogen and hydrogen; iron is not typically used in catalytic cracking
• Copper catalysts


  Facilitate the transfer of electrons, such as in the reduction of nitrogen oxides in automotive exhaust systems; copper is not typically used in catalytic cracking
• Silver catalysts


  Facilitate the transfer of oxygen atoms between molecules in oxidation reactions; silver is not typically used in catalytic cracking
• Zeolite catalysts


  Made up of tiny, porous crystals with a high surface area; pore size can be tailored to specific applications; commonly used in catalytic cracking
• Thermal cracking pressure


  7000 kilopascals (kPa), 7 megapascals (MPa), 1000 pounds per square inch (psi)
• Thermal cracking feedstock


  Heavy hydrocarbon mixture, such as vacuum gas oil or residual fuel oil
• Thermal cracking products


  Alkenes, alkanes, aromatics, gases (hydrogen, methane, ethane)