Alkanes

• What are alkanes classified as?

  Saturated hydrocarbons
• What is the general formula for alkanes?

  C$n$H$2n+$$2$
• How many times are alkanes bonded to hydrogen?

  Four times
• What is the general formula for cycloalkanes?

  C$n$H$2n$
• Where are cycloalkanes commonly found?

  In crude oil
• What is crude oil composed of?

  A mixture of different length hydrocarbons
• What are the main fractions obtained from fractional distillation of crude oil?

  • Gas (1-4 carbons)
  • Gasoline (5-10 carbons)
  • Kerosene (11-15 carbons)
  • Diesel oil (16-19 carbons)
  • Fuel oil (20-40 carbons)
  • Lubricating oil (40+ carbons)
• What is the temperature gradient in a fractional distillation column?

  Cooler at the top
• Why do different parts of the mixture condense at different temperatures during fractional distillation?

  Because there are different chain lengths and different boiling points
• What is LPG used for?

  Gas
• What is kerosene used for?

  Jet fuel and heating
• What is diesel oil used for?

  Diesel fuel
• What is fuel oil used for?

  Ships and power stations
• What is bitumen used for?

  Roofing and tarmac
• How do straight chain hydrocarbons affect boiling points?

  They pack tightly, increasing boiling points due to intermolecular forces
• How does the length of carbon chains affect boiling points?

  Longer chains have more electrons and stronger intermolecular forces, increasing boiling points
• How do branched chain alkanes compare to straight chain alkanes in terms of boiling points?

  Branched alkanes have lower boiling points compared to their straight chain counterparts
• What is cracking in the context of hydrocarbons?

  • Turning long chain hydrocarbon fractions into smaller chain hydrocarbons
  • Smaller chain hydrocarbons are more useful and in greater demand
• What are the conditions for thermal cracking?

  High temperatures (1000°C) and high pressures (70 atm)
• What are the main products of thermal cracking?

  Mainly alkenes
• What is propene used to make?

  Poly(propene)
• What are the conditions for catalytic cracking?

  High temperature (450°C) and slight pressure
• What catalyst is used in catalytic cracking?

  Zeolite catalyst
• How does using a zeolite catalyst benefit catalytic cracking?

  It lowers the temperature and pressure needed for cracking
• What is the conservation of mass in the context of cracking?

  The mass at the start of the reaction is the same as the mass at the end
• Why are alkanes considered good fuels?

  They burn readily to produce large amounts of energy
• What happens during complete combustion of alkanes?

  They burn cleanly and completely forming CO₂ and water
• What is the balanced equation for the complete combustion of methane?

  CH₄ + 2O₂ → CO₂ + 2H₂O
• What occurs during incomplete combustion of alkanes?

  They burn with a limited supply of oxygen, producing carbon monoxide or soot and water
• What is the balanced equation for the incomplete combustion of butane producing carbon monoxide?

  C₄H₁₀ + 4.5O₂ → 4CO + 5H₂O
• What is the balanced equation for the incomplete combustion of butane producing soot?

  C₄H₁₀ + 2.5O₂ → 4C + 5H₂O
• What are the environmental problems associated with combustion of fossil fuels?

  • Global warming due to CO₂ emissions
  • Acid rain from sulfur dioxide emissions
  • Incomplete combustion leading to carbon monoxide and soot
• How does CO₂ contribute to global warming?

  It absorbs infrared radiation and emits some back to the Earth
• What is acid rain and how is it formed?

  Acid rain is formed from sulfur dioxide released during combustion, leading to sulfuric acid
• What are the effects of acid rain?

  It damages plants, erodes buildings, and kills fish
• Why is carbon monoxide dangerous?

  It bonds to hemoglobin in the blood, preventing oxygen bonding
• What are the effects of soot from incomplete combustion?

  Soot causes breathing problems, global dimming, and clogs up engines
• What is the process of converting alkanes to haloalkanes called?

  Free Radical Substitution
• What are radicals?

  Substances that contain an unpaired electron in the outer shell
• What conditions are required for the initiation of free radical substitution?

  UV light and room temperature