By which unit do the successive members of the homogenous series CH₄, C₂H₆, and C₃H₈ differ from each other? 

The Correct answer is CH₂.

Key Points

• The successive members of a homologous series differ by a common unit, which is CH₂.
• A homologous series is a group of organic compounds that have a similar structure and functional group but differ by a fixed unit in their molecular formula.
• In the series provided (CH₄, C₂H₆, C₃H₈), the molecular formulas show a successive difference of CH₂ units between each compound.
• The molecular formula of methane (CH₄) and ethane (C₂H₆) differs by one CH₂ unit, and similarly, ethane (C₂H₆) and propane (C₃H₈) also differ by one CH₂ unit.
• Each member of a homologous series has similar chemical properties but shows a gradual change in physical properties like boiling point, melting point, and density due to the addition of the CH₂ group.
• The concept of homologous series is crucial in organic chemistry as it simplifies the study of organic compounds by grouping them into families.

 Additional Information

• CH₄
  • CH₄, also known as methane, is the simplest alkane and the first member of the alkane homologous series.
  • Methane is a major component of natural gas and is widely used as a fuel source.
  • It is a colorless, odorless gas at room temperature and is a potent greenhouse gas.
• CH
  • CH is not a stable molecule in the context of hydrocarbons and does not represent a homologous series unit.
  • It is a radical and may exist in some transient chemical reactions.
• CH₃
  • CH₃ is a methyl group, which is a part of many organic compounds but does not represent the common difference in a homologous series.
  • It is often seen as a substituent or functional group in organic chemistry.