Alkanes

• Why are C-H bonds in alkanes considered non-polar?

  Similar electronegativities
• Alkanes have a simple molecular structure with Van der Waals forces between the molecules
• What type of intermolecular forces are found in alkanes?

  Van der Waals forces
• Alkanes are soluble in water.

  False
• As the length of the carbon chain increases, the boiling point of the alkane increases
• Why do longer alkanes have higher boiling points?

  Stronger Van der Waals forces
• Order the following isomers of pentane by boiling point from highest to lowest:

  1️⃣ Pentane

  2️⃣ 2-methylbutane

  3️⃣ 2,2-dimethylpropane
• What happens to the boiling point of alkanes as the number of branches increases?

  Decreases
• Branched alkanes have lower boiling points due to fewer points of contact
• Crude oil is mainly composed of alkane hydrocarbons.
• What is the process called that separates crude oil into fractions based on boiling points?

  Fractional distillation
• The hydrocarbons with the lowest boiling points are drawn off as gases
• What happens to the largest hydrocarbons in the fractional distillation process?

  Collected as residue
• What is the process called that converts longer alkanes into more useful molecules by breaking C-C bonds?

  Cracking
• Match the type of cracking with its conditions:

  Thermal cracking ↔️ High temperature and pressure

  Catalytic cracking ↔️ High temperature, slight pressure, zeolite catalyst
• What type of products are formed during thermal cracking of alkanes?

  Alkanes and alkenes
• Catalytic cracking produces cycloalkanes, branched alkanes, and aromatic hydrocarbons such as benzene
• The products of alkane combustion depend on the supply of oxygen.
• What are the products of complete combustion of alkanes?

  Carbon dioxide and water
• What are the products of incomplete combustion of alkanes?

  Carbon monoxide and water
• Incomplete combustion occurs when there is a limited supply of oxygen.
• Match the pollutant with its effect:

  Unburned hydrocarbons ↔️ Low level ozone

  Carbon dioxide ↔️ Global warming

  Carbon monoxide ↔️ Toxic gas

  Nitrogen oxides ↔️ Acid rain and smog
• What is the primary purpose of a catalytic converter in a car exhaust system?

  Remove pollutants
• Catalytic converters contain a honeycombed structure coated with metals such as Pt, Pd, and Rh
• Flue gas desulfurisation uses calcium oxide or calcium carbonate to absorb sulfur dioxide.
• What type of reaction occurs when alkanes react with halogens?

  Substitution
• The reaction between an alkane and a halogen requires the condition of UV light
• What type of isomers are formed when alkanes with three or more carbons react with a halogen?

  Position isomers
• Further substitution reactions can occur with halogenoalkanes.