Question

Successive alkanes differ by :

• A. CH\(_2\)
• B. CH
• C. CH\(_3\)
• D. C\(_2\)H\(_4\)

Hint:

All homologous series (alkanes, alkenes, alcohols, etc.) differ by \(CH_2\).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Alkanes form a homologous series. A homologous series is a group of organic compounds having the same functional group and similar chemical properties in which successive members differ by a specific repeating unit.
Step 2: Detailed Explanation:
The general formula for alkanes is \( \text{C}_{n}\text{H}_{2n+2} \).
- For \( n=1 \): \( \text{CH}_{4} \) (Methane)
- For \( n=2 \): \( \text{C}_{2}\text{H}_{6} \) (Ethane)
- For \( n=3 \): \( \text{C}_{3}\text{H}_{8} \) (Propane)
Difference between Ethane and Methane: \( \text{C}_{2}\text{H}_{6} - \text{CH}_{4} = \text{CH}_{2} \)
Difference between Propane and Ethane: \( \text{C}_{3}\text{H}_{8} - \text{C}_{2}\text{H}_{6} = \text{CH}_{2} \)
In terms of mass, this corresponds to a difference of \( 12 + 2 = 14 \text{ atomic mass units} \).
Step 3: Final Answer:
Successive members of the alkane homologous series differ by a \( \text{CH}_{2} \) group.