Compounds C_2 H_6 and C_3 H_8 are differ by unit and belong to series.

Correct option is D

The correct answer is (D) CH₂, homologous.

Explanation:

• Homologous Series:
• A homologous series is a group of organic compounds that have the same functional group and similar chemical properties but differ by a fixed CH₂ unit between consecutive members.
• C₂H₆ (Ethane) and C₃H₈ (Propane):
• These compounds belong to the alkane family (CnH2n+2).
• They differ by one CH₂ unit:
1. Ethane (C₂H₆) → Propane (C₃H₈): Difference = CH₂.
• Correct Characteristics:
• They belong to a homologous series because:
1. They follow the same general formula (CnH2n+2).
2. Their physical properties vary gradually.
3. They exhibit similar chemical behavior.

Clarifications for Other Options:

• CH₃, homologous: Incorrect, as the difference is CH₂, not CH₃.
• CH₂, heterogeneous: Incorrect, as they are in a homologous series, not heterogeneous.
• CH₃, heterogeneous: Incorrect, as both the difference and classification are wrong.