Question

In the structure of the dichromate ion, there is a :

• A. linear symmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.
• B. linear unsymmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.
• C. non-linear symmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.
• D. non-linear unsymmetrical \( \text{Cr}-\text{O}-\text{Cr} \) bond.

Hint:

Dichromate ions are stable in acidic medium, whereas chromate ions (\( \text{CrO}_4^{2-} \)) are stable in basic medium. The transition occurs via the \( \text{Cr}-\text{O}-\text{Cr} \) bridge formation.

Answer 1

The Correct Option is C

The question deals with the molecular structure of the dichromate ion, particularly focusing on the nature of the \text{Cr}-\text{O}-\text{Cr} bond. Let's analyze the structure and the bonding within the dichromate ion to determine the correct option.

The dichromate ion, with the formula \text{Cr}_2\text{O}_7^{2-}, consists of two chromium atoms and seven oxygen atoms. In the dichromate ion, the structure contains a bridge of oxygen atoms between two chromium centers:

1. Each chromium atom is surrounded by oxygen atoms in a tetrahedral arrangement, sharing one oxygen atom in a bridge with another chromium atom.

2. There is a \text{Cr}-\text{O}-\text{Cr} bridge where the bridging oxygen atom is equidistant from both chromium atoms. This means that the bond is symmetrical.

3. The angle in the \text{Cr}-\text{O}-\text{Cr} bridge is non-linear, as the structure isn't a straight line.

Given these points, the structure of the dichromate ion has a non-linear symmetrical \text{Cr}-\text{O}-\text{Cr} bond.

Conclusion: The correct option is that the dichromate ion contains a non-linear symmetrical \text{Cr}-\text{O}-\text{Cr} bond.