In which of the following compounds `B-O` bond length is shortest?

Options

A. `H_(3)BO_(3)`
B. `B(OH)_(4)`
C. Both have same
D. None

Explanation

To determine which compound has the shortest B-O bond length, we will analyze the bond lengths in the given compounds, specifically H3BO3 (boric acid) and B(OH)4 (tetrahydroxyborate).

### Step-by-Step Solution:

1. **Identify the Compounds**:
We need to compare the bond lengths of B-O in H3BO3 and B(OH)4.

2. **Understand the Structure**:
- **H3BO3 (Boric Acid)**: This compound has a trigonal planar structure where boron is bonded to three hydroxyl groups (-OH).
- **B(OH)4 (Tetrahydroxyborate)**: This compound has a tetrahedral structure where boron is bonded to four hydroxyl groups.

3. **Consider Bond Order**:
- The bond order is an important factor in determining bond length. A higher bond order typically results in shorter bond lengths.
- In H3BO3, the B-O bonds are single bonds (bond order = 1).
- In B(OH)4, the B-O bonds are also single bonds, but the presence of more hydroxyl groups can lead to increased electron repulsion.

4. **Analyze Electron Repulsion**:
- In B(OH)4, the tetrahedral arrangement means that there are more bond pairs of electrons around the boron atom. This can lead to increased electron-electron repulsion, which can cause the bond lengths to be longer to minimize this repulsion.
- In contrast, H3BO3 has fewer bond pairs, leading to less repulsion and thus shorter bond lengths.

5. **Conclusion**:
Based on the analysis, the B-O bond length in H3BO3 is shorter than that in B(OH)4 due to the reduced electron repulsion in the trigonal planar structure compared to the tetrahedral structure.

Therefore, the compound with the shortest B-O bond length is **H3BO3**.

### Final Answer:
**H3BO3 (Boric Acid)** has the shortest B-O bond length.