Question

Which among the following statement is NOT true about homologous series of organic compounds?

• A. Each member of a series differs by two carbon atoms and two H atoms from neighbouring member.
• B. All members have similar chemical properties.
• C. All members of series have same type of carbon skeleton.
• D. All members of series are represented by same general formula.

Hint:

To spot the error instantly, look at a real example like methane ($\mathrm{CH}_4$) and ethane ($\mathrm{C}_2\mathrm{H}_6$). The difference between them is exactly $1\ \mathrm{C}$ and $2\ \mathrm{H}$ atoms ($-\mathrm{CH}_2-$). Any statement claiming a jump of two carbon atoms is an immediate error.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The problem lists four structural and behavioral traits of a chemical homologous series and requires identifying the statement that is factually false.

Step 2: Detailed Explanation:
Let's evaluate the chemical definitions of a homologous series item by item: Option (B): True. Members share the exact same functional group, which directly determines their chemical reactivity and properties. Option (C): True. The foundational style of the carbon skeleton (e.g., straight-chain alkanes) remains consistent as you walk down the series. Option (D): True. Every series follows an overarching general mathematical formula (e.g., $\mathrm{C}_n\mathrm{H}_{2n+2}$ for alkanes). Option (A): False. By definition, consecutive or neighboring members in a homologous series change by a single structural methylene group, which is a $-\mathrm{CH}_2-$ unit. This means they differ by exactly one carbon atom and two hydrogen atoms, not two of each.

Step 3: Final Answer:
The statement that is not true is option (A).