Assertion : The experimentally determined carbon to oxygen bond length in carbon dioxide is 115 pm.
Reason : The lengths of a normal carbon to oxygen double bond `(C=O)` and carbon to oxygen triple bond `(C-=)` are 121 pm and 110 pm respectively.

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

Explanation

To solve the assertion and reason question, we will analyze both the assertion and the reason step by step.

### Step 1: Analyze the Assertion
The assertion states that the experimentally determined carbon to oxygen bond length in carbon dioxide (CO2) is 115 picometers (pm).

- **Understanding Carbon Dioxide Structure**: In CO2, carbon is double bonded to each oxygen atom. The bond length is influenced by the nature of the bonds involved.

### Step 2: Analyze the Reason
The reason provided states that the lengths of a normal carbon to oxygen double bond (C=O) and carbon to oxygen triple bond (C≡O) are 121 pm and 110 pm, respectively.

- **Understanding Bond Lengths**: The bond lengths indicate that a double bond (C=O) is longer than a triple bond (C≡O). The bond length of 121 pm for C=O is longer than the bond length of 110 pm for C≡O, which is consistent with the general trend that triple bonds are shorter than double bonds.

### Step 3: Compare the Assertion and Reason
Now we compare the assertion and the reason:

- The bond length of 115 pm in CO2 is indeed shorter than the C=O bond length (121 pm) and longer than the C≡O bond length (110 pm). This suggests that the bond length in CO2 is an average of the two bond types due to resonance.

### Step 4: Conclusion
Both the assertion and reason are correct statements. However, the reason does not directly explain why the bond length in CO2 is 115 pm; it merely states the bond lengths of C=O and C≡O. Therefore, the correct conclusion is that while both statements are true, the reason does not serve as the correct explanation for the assertion.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Correct Option**: B (Both assertion and reason are true, but reason is not the correct explanation of assertion).