Among the given species the one which contains weakest carbon - oxygen bond : `CO_2,CH_3COO^(-),CO,CO_3^(2-)`

Options

A. `CO_2`
B. `CH_3COO^-`
C. CO
D. `CO_3^(2-)`

Answer

To determine which of the given species has the weakest carbon-oxygen bond among `CO2`, `CH3COO^(-)`, `CO`, and `CO3^(2-)`, we need to analyze the bond order for each species. The bond order is a measure of the number of chemical bonds between a pair of atoms and is directly related to bond strength: the lower the bond order, the weaker the bond.

### Step-by-Step Solution:

1. **Analyze CO2 (Carbon Dioxide)**:
- The Lewis structure of CO2 shows that carbon is double bonded to each oxygen atom.
- There are two bonds between carbon and oxygen in this molecule.
- Since there are no resonance structures affecting the bond order, the bond order for CO2 is:
\[ \text{Bond Order} = \frac{\text{Number of bonds}}{\text{Number of structures}} = \frac{2}{1} = 2 \]

2. **Analyze CH3COO^(-) (Acetate Ion)**:
- The acetate ion has resonance structures. In one structure, carbon is double bonded to one oxygen and single bonded to another oxygen which carries a negative charge.
- The bond order can be calculated as follows:
- In one resonance structure, there are 2 bonds (double bond) and in another, there is 1 bond (single bond).
- Therefore, the bond order is:
\[ \text{Bond Order} = \frac{2 + 1}{2} = \frac{3}{2} = 1.5 \]

3. **Analyze CO (Carbon Monoxide)**:
- In CO, carbon and oxygen are triple bonded, which includes one coordinate bond.
- The bond order for CO is:
\[ \text{Bond Order} = 3 \]

4. **Analyze CO3^(2-) (Carbonate Ion)**:
- The carbonate ion has three resonance structures. In these structures, one oxygen is double bonded to carbon, while the other two are single bonded.
- The bond order can be calculated as follows:
- For each resonance structure, the bond counts are 2 (double bond) and 1 (single bond) for two structures.
- Therefore, the bond order is:
\[ \text{Bond Order} = \frac{2 + 1 + 1}{3} = \frac{4}{3} \approx 1.33 \]

5. **Comparison of Bond Orders**:
- CO2: Bond Order = 2
- CH3COO^(-): Bond Order = 1.5
- CO: Bond Order = 3
- CO3^(2-): Bond Order = 1.33

6. **Conclusion**:
- The species with the weakest carbon-oxygen bond is the one with the lowest bond order.
- Therefore, the weakest carbon-oxygen bond is found in the carbonate ion (CO3^(2-)), with a bond order of approximately 1.33.

### Final Answer:
The species that contains the weakest carbon-oxygen bond is **CO3^(2-)**.

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