In the anion `HCOO^-` , the carbon-oxygen bonds are found to be of equal length. This is due to :

Options

A. The anion is obtained by the removal of a proton from the acid molecule.
B. Electronic orbitals of carbon atoms are hybridised.
C. The `C=O` bond is weaker than `C-O` bond.
D. The anion `HCOO^(-)` has two equally stable resonating structures.

Explanation

To solve the question regarding the equal bond lengths in the anion `HCOO^-`, we can follow these steps:

### Step 1: Understand the structure of the formate anion
The formate anion, `HCOO^-`, consists of a carbon atom bonded to two oxygen atoms and one hydrogen atom. The carbon atom is at the center, with one oxygen atom double-bonded to it and the other oxygen atom single-bonded to it.

### Step 2: Draw the Lewis structure
The Lewis structure of the formate anion can be represented as:
```
O
||
H - C - O^(-)
```
Here, one oxygen has a double bond with carbon (C=O), and the other oxygen has a single bond with carbon (C-O). The single-bonded oxygen carries a negative charge.

### Step 3: Consider resonance structures
The formate anion can exhibit resonance. This means that the double bond and the negative charge can shift between the two oxygen atoms. The resonance structures can be represented as:
1. Structure 1:
```
O
||
H - C - O^(-)
```
2. Structure 2:
```
O^(-)
|
H - C = O
```

### Step 4: Determine the hybrid structure
The actual structure of the formate anion is a hybrid of these resonance structures. This hybrid structure has characteristics of both forms, meaning that both carbon-oxygen bonds are neither purely single nor purely double bonds.

### Step 5: Conclude about bond lengths
Due to resonance, the carbon-oxygen bonds in the formate anion are of equal length. This bond length is intermediate between that of a single bond (C-O) and a double bond (C=O). Therefore, both carbon-oxygen bonds are equal in length because of the delocalization of electrons.

### Final Answer
The equal bond lengths in the anion `HCOO^-` are due to resonance, which allows the double bond character to be shared between the two carbon-oxygen bonds.

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