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

Concept: Alkanes belong to a homologous series with general formula: \[ C_nH_{2n+2} \] Members of a homologous series differ by a constant unit.

Step 1: Write two successive alkanes.
\[ \text{First: } C_nH_{2n+2} \] \[ \text{Next: } C_{n+1}H_{2(n+1)+2} = C_{n+1}H_{2n+4} \]

Step 2: Find the difference.
\[ C_{n+1}H_{2n+4} - C_nH_{2n+2} = C_1H_2 = CH_2 \]

Step 3: Verification using examples.
\[ CH_4 \rightarrow C_2H_6 \rightarrow C_3H_8 \] \[ \text{Each step increases by } CH_2 \] Conclusion:
Successive alkanes differ by a \(CH_2\) group.