Which of the following statements are not correct

Options

A. All C–O bonds in `CO_3^(2–)` are equal but not in `H_2CO_3`
B. All C-O bonds in `HCO_2^-` are equal but not in `HCO_2H`
C. C-O bond length in `HCO_2^-` is longer than C-O bond length in `CO_3^(2-)`
D. C-O bond length in `HCO_2^(-)` and C-O bond length in `CO_3^(2-) ` are equal

Answer

To determine which statements are not correct regarding the bond lengths and bond orders in the given compounds, we can analyze the information provided step by step.

### Step 1: Understanding Bond Order and Bond Length
Bond order is defined as the number of bonds between two atoms in a molecule. It is calculated by taking the total number of bonds from all resonance structures and dividing it by the number of resonance structures. Higher bond order corresponds to shorter bond lengths, while lower bond order corresponds to longer bond lengths.

### Step 2: Analyzing CO3^2- (Carbonate Ion)
- The carbonate ion (CO3^2-) has three resonance structures.
- The bond order for the C-O bonds in CO3^2- is calculated as follows:
- Total bonds = 4 (2 from one resonance structure and 1 from each of the other two)
- Total resonance structures = 3
- Bond order = Total bonds / Total resonance structures = 4 / 3 = 1.33
- All C-O bonds in CO3^2- are equal due to resonance stabilization.

### Step 3: Analyzing H2SO3 (Sulfurous Acid)
- In H2SO3, the bond order of the C-O bonds is not equal due to the presence of a double bond and single bonds.
- The bond order for the C=O bond is 2, while the bond order for the C-O (single bond) is 1.
- Therefore, the bond lengths will also differ, with the C=O bond being shorter than the C-O bonds.

### Step 4: Analyzing HCO2^- (Formate Ion)
- The formate ion (HCO2^-) has two resonance structures.
- The bond order for the C-O bonds in HCO2^- is calculated as follows:
- Total bonds = 3 (1 double bond and 1 single bond)
- Total resonance structures = 2
- Bond order = 3 / 2 = 1.5
- The bond lengths in HCO2^- are equal because the bond order is the same for both C-O bonds.

### Step 5: Comparing Bond Lengths
- For CO3^2-, the bond length is shorter due to a higher bond order (1.33).
- For HCO2^-, the bond length is longer due to a bond order of 1.5.
- The bond length in HCO2^- is longer than in CO3^2-.

### Step 6: Conclusion on Incorrect Statements
Based on the analysis:
1. All C-O bonds in CO3^2- are equal (correct).
2. C-O bonds in H2SO3 are not equal (correct).
3. C-O bonds in HCO2^- are equal (correct).
4. The bond length in HCO2^- is longer than in CO3^2- (correct).
5. The bond length in HCO2^- is equal to the bond length in CO3^2- (incorrect).

### Final Answer
The statement that is not correct is that the bond lengths in HCO2^- and CO3^2- are equal.

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