Assertion :In `ch_2=c=ch_2` all the carbon atmos are sp2 hybridised. Reason: All the hydrpogen atoms lie in one plane

Options

A. If both assertion and reason are correct and reason is crect explanation for assertion
B. If both assertion and reason are correct but reason is not cottect explanation for assertion
C. If reason is correct but assertion is incorrect
D. If both assertion and reason are incorrect

Answer

To solve the question regarding the assertion and reason related to the hybridization of carbon atoms in the molecule CH2=C=CH2, we will analyze each part step by step.

### Step 1: Analyze the Assertion
The assertion states that "In CH2=C=CH2 all the carbon atoms are sp² hybridized."

- **Hybridization of Carbon Atoms**:
- In the molecule CH2=C=CH2 (also known as allene), we have two double bonds between the carbon atoms.
- The central carbon atom (C2) is bonded to two other carbon atoms (C1 and C3) through double bonds and has no hydrogen atoms attached.
- The terminal carbon atoms (C1 and C3) each have two hydrogen atoms and one double bond with the central carbon (C2).

- **Determining Hybridization**:
- For C1 and C3 (terminal carbons), they are bonded to two hydrogen atoms and one carbon atom through a double bond. This gives them three regions of electron density, leading to sp² hybridization.
- For C2 (central carbon), it is bonded to two carbon atoms (C1 and C3) through double bonds, which gives it two regions of electron density, leading to sp hybridization.

**Conclusion for Assertion**: The assertion is incorrect because not all carbon atoms in CH2=C=CH2 are sp² hybridized; C2 is sp hybridized.

### Step 2: Analyze the Reason
The reason states that "All the hydrogen atoms lie in one plane."

- **Molecular Geometry**:
- In the structure of CH2=C=CH2, the terminal carbon atoms (C1 and C3) have their hydrogen atoms in the same plane as the carbon atoms (due to sp² hybridization).
- However, the central carbon atom (C2) has its two hydrogen atoms positioned above and below the plane of the molecule due to the sp hybridization.

**Conclusion for Reason**: The reason is also incorrect because not all hydrogen atoms lie in the same plane; some are above and some are below the plane.

### Final Conclusion
Both the assertion and the reason are incorrect. Therefore, the correct option is D: "Both assertion and reason are incorrect."

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