Two research students were instruced intructed to synthesise the complex
`[Co(NH_(3))_(5)(NO_(2))]Br_(2)`
They synthesised the complexes with identical molecular formula molar mass geometry conductane and spin but they differed in colour Based on the above facts answer the following questions
The difference in colour is due to

Options

A. optical isomerism
B. geometrical isomerism
C. linkage isomerism
D. nuclear isomerism

Answer

To determine the reason for the difference in color of the two complexes `[Co(NH₃)₅(NO₂)]Br₂`, we can analyze the situation step by step.

### Step 1: Understanding the Complex
The complex in question is `[Co(NH₃)₅(NO₂)]Br₂`. It consists of a cobalt ion (Co) surrounded by five ammonia (NH₃) ligands and one nitrito (NO₂) ligand, with two bromide (Br) ions as counterions.

**Hint:** Identify the components of the complex and their roles.

### Step 2: Identifying the Isomerism
The problem states that the two synthesized complexes have identical molecular formulas, molar masses, geometries, conductance, and spins. However, they differ in color. This suggests that the difference in color is due to isomerism.

**Hint:** Consider the types of isomerism that can occur in coordination compounds.

### Step 3: Linkage Isomerism
In coordination chemistry, linkage isomerism occurs when a ligand can coordinate to the metal ion in more than one way. The nitrito ligand (NO₂) can bind through either the nitrogen (N) or the oxygen (O) atom. This leads to two different isomers of the same complex:

1. **Nitro Isomer**: When NO₂ binds through nitrogen (N).
2. **Nitrito Isomer**: When NO₂ binds through oxygen (O).

**Hint:** Think about how the different binding sites of the same ligand can affect the properties of the complex.

### Step 4: Color Difference
The difference in the way the nitrito ligand coordinates to the cobalt ion can lead to different electronic environments around the metal ion, which can affect the absorption of light. As a result, the two isomers can exhibit different colors due to their different electronic transitions.

**Hint:** Remember that color in coordination compounds is often related to the d-orbital splitting and the specific wavelengths of light absorbed.

### Conclusion
The difference in color between the two synthesized complexes is due to **linkage isomerism**. The nitrito ligand can coordinate through either nitrogen or oxygen, resulting in two distinct isomers that absorb light differently.

**Final Answer:** The difference in color is due to linkage isomerism.