Assertion: Alkanes containing more than three carbon atoms exhibit chain isomerism.
Reason: In an alkane, all carbon atoms are `sp^(3)` hybridised.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To analyze the assertion and reason provided in the question, we can break it down step by step.

### Step 1: Understand the Assertion
The assertion states that "Alkanes containing more than three carbon atoms exhibit chain isomerism."

**Explanation**:
- Chain isomerism occurs when compounds have the same molecular formula but different arrangements of carbon atoms in a chain.
- For alkanes, which are saturated hydrocarbons, this type of isomerism becomes possible when there are enough carbon atoms to allow for branching.
- Alkanes with four or more carbon atoms can have different structural forms (isomers) due to the ability to branch off the main carbon chain.

### Step 2: Understand the Reason
The reason states that "In an alkane, all carbon atoms are sp³ hybridized."

**Explanation**:
- In alkanes, each carbon atom forms four single bonds (sigma bonds) with other atoms (either carbon or hydrogen).
- This bonding arrangement requires sp³ hybridization, where one s orbital and three p orbitals mix to form four equivalent sp³ hybrid orbitals.
- This hybridization is characteristic of alkanes, as it allows for the tetrahedral geometry around each carbon atom.

### Step 3: Evaluate the Relationship Between Assertion and Reason
- Both the assertion and the reason are true statements.
- However, the reason does not explain the assertion. The fact that carbon atoms in alkanes are sp³ hybridized is a general characteristic of alkanes but does not directly relate to the occurrence of chain isomerism.

### Conclusion
Based on the analysis:
- The assertion is true: Alkanes with more than three carbon atoms do exhibit chain isomerism.
- The reason is also true: All carbon atoms in alkanes are sp³ hybridized.
- However, the reason does not provide an explanation for the assertion.

### Final Answer
Both the assertion and the reason are correct, but the reason does not explain the assertion. Therefore, the correct option is:
**B: Both assertion and reason are correct, but reason does not explain the assertion.**

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