Homologous Series

• What is the general formula for alkanes?

  $C_nH_{2n+2}$
• What is the definition of a homologous series?

  • Family of compounds
  • Same general formula
  • Similar chemical properties
• What are two characteristics of members of the same homologous series?

  • Same general formula
  • Similar chemical properties
• What is the general formula for cycloalkynes?

  $C_nH_{2n-2}$
• What are hydrocarbons?

  Compounds that contain only carbon and hydrogen atoms.
• What are the steps to work out the general formula for a homologous series?

  Write the molecular formula for each member, stack them by increasing carbon chain length, start with $C_nH_{2n}$ and adjust hydrogens to fit the trends.
• Why do cycloalkanes have the same general formula as alkenes?

  Because their structure includes a ring, which reduces hydrogen atoms similar to a double bond.
• How is the general formula for alkynes derived?

  By subtracting two hydrogen atoms from the alkanes general formula, yielding $C_nH_{2n-2}.$
• What is a homologous series?

  A family of compounds with the same general formula and similar chemical properties.
• What are the hydrocarbon families studied in chemistry?

  • Alkanes
  • Alkenes
  • Cycloalkanes
• Why does the general formula for alkenes include only $2n$ hydrogen atoms?


  Because the presence of a double bond reduces the number of hydrogen atoms needed by $2n.$
• What are the components of liquefied petroleum gas (LPG)?

  Propane and butane.
• What distinguishes alkynes from other hydrocarbons?

  They contain a carbon-carbon triple bond.
• What are hydrocarbons and what do they contain?

  • Hydrocarbons are organic compounds containing only carbon and hydrogen atoms.
• What does the ending '-ane' indicate in hydrocarbon names?

  • Single carbon-carbon bonds in alkanes.
• What type of carbon-carbon bonds are present in alkanes?

  Carbon-carbon single bonds
• What term describes alkanes based on their carbon-carbon bonding?

  Saturated
• What is the general formula for alkanes?

  $C_nH_{2n+2}$
• What does the prefix in the name of an alkane represent?

  The number of carbon atoms in the longest chain.
• List the prefixes for alkanes with one to eight carbon atoms.

  • Meth: 1 carbon
  • Eth: 2 carbons
  • Prop: 3 carbons
  • But: 4 carbons
  • Pent: 5 carbons
  • Hex: 6 carbons
  • Hept: 7 carbons
  • Oct: 8 carbons
• How many carbon atoms does the prefix 'meth' indicate?

  One carbon atom.
• How many carbon atoms does the prefix 'eth' indicate?

  Two carbon atoms.
• How many carbon atoms does the prefix 'but' indicate?

  Four carbon atoms.
• How many carbon atoms does the prefix 'prop' indicate?

  Three carbon atoms.
• How many carbon atoms does the prefix 'pent' indicate?

  Five carbon atoms.
• How many carbon atoms does the prefix 'hex' indicate?

  Six carbon atoms.
• How many carbon atoms does the prefix 'hept' indicate?

  Seven carbon atoms.
• How many carbon atoms does the prefix 'oct' indicate?

  Eight carbon atoms.
• What is the first member of the alkane homologous series?

  • Methane.
• How do you convert the full structural formula of an alkane into the shortened structural formula?

  • Remove the physical bonds from the full structural formula.
• What is the shortened structural formula for methane?

  $CH_4$
• What is the overall molecular formula for methane?

  $CH_4$
• How many carbon and hydrogen atoms are in the molecular formula for methane?

  • One carbon atom and four hydrogen atoms.
• What is the name of the second member of the alkane homologous series?

  • Ethane.
• How many carbon atoms are present in ethane?

  Two carbon atoms.
• What does saturated mean in the context of hydrocarbons?

  Having only single carbon-carbon bonds.
• How do you draw the full structural formula for ethane?

  • Connect two carbon atoms with a single bond.
  • Attach three hydrogen atoms to each carbon atom.
• What is the shortened structural formula for ethane?

  $CH_3CH_3$
• What is the molecular formula for ethane?

  $C_2H_6$
• How many carbon and hydrogen atoms are present in ethane?

  • Two carbon atoms and six hydrogen atoms.