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QuestionChemistry

Which of the following resonance structures for OCN− will contribute most to the correct structure of OCN−? A. O=C=N, with one lone pair on O, two lone pairs on C, and one lone pair on N B. O−C≡N, with three lone pairs on O and one lone pair on N C. O≡C−N, with one lone pair on O and three lone pairs on N D. O=C=N, with two lone pairs on O and two lone pairs on N E. They all contribute equally to the correct structure of OCN− .
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Answer

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Step 1:
Let's solve this step by step:

Step 2:
: Analyze the Resonance Structures

To determine which resonance structure contributes most, we need to consider: - Formal charges - Electron distribution - Electronegativity of atoms - Stability of the structure

Step 3:
: Calculate Formal Charges

\text{Formal Charge} = \text{Valence Electrons} - \text{Lone Pair Electrons} - \frac{1}{2}\text{Bonding Electrons}
For each structure, we'll calculate the formal charge using the formula:

Step 4:
: Evaluate Option A

\text{N: } 5 - 1 - \frac{1}{2}(4) = 1
\text{C: } 4 - 4 - \frac{1}{2}(4) = 0 This structure has minimal charge separation.

Step 5:
: Evaluate Option B

\text{N: } 5 - 1 - \frac{1}{2}(2) = 3
\text{C: } 4 - 2 - \frac{1}{2}(4) = 1 This structure has significant charge separation.

Step 6:
: Evaluate Option C

\text{N: } 5 - 3 - \frac{1}{2}(2) = 1
\text{C: } 4 - 2 - \frac{1}{2}(4) = 1 This structure has extreme charge separation.

Step 7:
: Evaluate Option D

\text{N: } 5 - 2 - \frac{1}{2}(4) = 1
\text{C: } 4 - 2 - \frac{1}{2}(4) = 0 Similar to Option A, but with different electron distribution.

Step 8:
: Conclusion

Option A (O=C=N) contributes most because: - Minimal formal charge - Symmetric electron distribution - Follows the octet rule - Minimizes charge separation

Final Answer

O=C=N, with one lone pair on O, two lone pairs on C, and one lone pair on N will contribute most to the correct structure of OCN−.