Question

State any four characteristics of a homologous series

State two characteristics of a homologous series.

Answer 1

Characteristics of a homologous series:

• Each member of the series differs from the preceding one by the addition of a -CH2 group and by 14 a.m.u.
• All members of a homologous series share the general formula.
  Example: The general formula for alkane is CnH2n+2 and alkene is CnH2n.
• The physical properties of the members show a gradation in properties as the molecular mass increases.
• The chemical properties also show a gradient similarity.
  Example: Methane and ethane react with chlorine to form methyl chloride and ethyl chloride, respectively.
  CH₄ + Cl₂ → CH₃Cl
  C₂H₆ + Cl₂ → C₂H₅Cl
• All members of a homologous series can be prepared by the same general method of preparation.
  Example: Alcohols can be prepared from alkyl halides.

          `CH_3Br+KOH " Boil"/""CH_3OH+KBr`

          `C_2H_5Br+KOH " Boil"/""C_2H_5OH+KBr`