Unit 2 ⚛️homologous series ⚛️

• What are hydrocarbons composed of?

  Hydrogen and carbon
• What is the general formula for alkanes?

  C$n$H$2n+$$2$
• What are the first five alkanes and their molecular formulas?

  1. Methane - CH₄
  2. Ethane - C₂H₆
  3. Propane - C₃H₈
  4. Butane - C₄H₁₀
  5. Pentane - C₅H₁₂
• What is the molecular formula for propane?

  C₃H₈
• What is the molecular formula for butane?

  C₄H₁₀
• What is the molecular formula for pentane?

  C₅H₁₂
• What is the molecular formula for hexane?

  C₆H₁₄
• What is the molecular formula for heptane?

  C₇H₁₆
• What is the molecular formula for octane?

  C₈H₁₈
• What distinguishes alkenes from alkanes?

  • Alkenes contain at least one carbon-to-carbon double bond.
  • Alkanes contain only single carbon-to-carbon bonds.
• What is the general formula for alkenes?

  C$n$H$2n$
• What are the first four alkenes and their molecular formulas?

  1. Ethene - C₂H₄
  2. Propene - C₃H₆
  3. Butene - C₄H₈
  4. Pentene - C₅H₁₀
• What is the molecular formula for ethene?

  C₂H₄
• What is the molecular formula for propene?

  C₃H₆
• What is the molecular formula for butene?

  C₄H₈
• What is the molecular formula for pentene?

  C₅H₁₀
• What are the characteristics of saturated and unsaturated hydrocarbons?

  • Saturated: Only single C-C bonds (alkanes, cycloalkanes)
  • Unsaturated: Contains double or triple bonds (alkenes)
• How can bromine solution be used to test for unsaturated hydrocarbons?

  Unsaturated compounds decolourise bromine solution.
• What is a homologous series?

  • A family of compounds with the same general formula.
  • Similar chemical properties.
  • Patterns in physical properties, such as melting and boiling points.
• What happens to melting and boiling points in a homologous series as the molecules get larger?

  They generally increase due to stronger intermolecular forces.
• What is the general formula for cycloalkanes?

  C$n$H$2n$
• What are the first four cycloalkanes?

  1. Cyclopropane
  2. Cyclobutane
  3. Cyclopentane
  4. Cyclohexane
• What is the definition of isomers?

  Compounds with the same molecular formula but different structural formulas.
• What are the uses of hydrocarbons?

  • Fuels
  • Alcohols
  • Solvents
• What is an addition reaction in hydrocarbons?

  Two or more molecules combine to form one product.
• What is the valency of carbon?


  4
• Why does methane have a significant role as a fuel?

  It is a useful fuel and is found in natural gas.
• What suffix do all alkanes have in their names?

  • ane
• What is the simplest alkane molecule?

  Methane
• What is the significance of the first member of the alkene family?

  It is ethene, as at least 2 carbons are needed for a double bond.
• What is used to indicate the position of the double bond in alkenes?

  A number is used to indicate the position of the double carbon-to-carbon bond.
• How are branched alkenes named?

  Branched alkenes are named in a similar way to branched alkanes.
• What is the procedure for naming alkenes?

  • Select the longest continuous chain of carbon atoms containing the double bond.
  • Number the carbon atoms from the end nearest the double bond.
  • Indicate the position of the double bond.
  • Name any branches and indicate their positions on the chain.
• What is the example given for naming an alkene?

  The example given is 3-methylbut-1-ene.
• What defines saturated hydrocarbons?

  Saturated hydrocarbons have all carbon-to-carbon bonds as single bonds.
• What are unsaturated hydrocarbons?

  Unsaturated hydrocarbons contain at least one double or triple carbon-to-carbon bond.
• Which hydrocarbon families are examples of saturated hydrocarbons?

  Alkanes and cycloalkanes are examples of saturated hydrocarbons.
• What is the use of alkenes?

  Alkenes are used to make polymers and alcohols.
• What is the general formula for hydrocarbons?

  The general formula is $C_nH_{2n+2}$ for alkanes.
• What happens during an addition reaction with alkenes?

  • Alkenes react to produce saturated molecules.
  • Two or more molecules combine to form one product.
  • The double bond is replaced by a single bond.