Homologous Series
Which of the following pairs represents two members of the same homologous series?
Select the correct option:
Solution
C₂H₆ and C₃H₈
A homologous series consists of organic compounds sharing the same general formula and functional group, with consecutive members differing by one –CH₂– unit (14 mass units). C₂H₆ (ethane) and C₃H₈ (propane) are both alkanes following the general formula CₙH₂ₙ₊₂ and differ by exactly one –CH₂– group — they are genuine homologs. CH₄ (alkane) and C₂H₄ (alkene) belong to different series with different general formulas. C₂H₄ and C₂H₆ have the same number of carbons but different hydrogen counts — they are structural isomers, not homologs. CH₃OH (alcohol) and CH₃COOH (carboxylic acid) belong to different functional group classes.
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About This Question
- Subject
- chemistry
- Chapter
- some basic principles of organic chemistry
- Topic
- homologous series
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
C₂H₆ and C₃H₈
A homologous series consists of organic compounds sharing the same general formula and functional group, with consecutive members differing by one –CH₂– unit (14 mass units). C₂H₆ (ethane) and C₃H₈ (propane) are both alkanes following the general formula CₙH₂ₙ₊₂ and differ by exactly one –CH₂– group — they are genuine homologs. CH₄ (alkane) and C₂H₄ (alkene) belong to different series with different general formulas. C₂H₄ and C₂H₆ have the same number of carbons but different hydrogen counts — they are structural isomers, not homologs. CH₃OH (alcohol) and CH₃COOH (carboxylic acid) belong to different functional group classes.
This easy difficulty chemistry question is from the chapter some basic principles of organic chemistry, covering the topic of homologous series. It appeared in the 2025 exam.
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