Which of the following complexes will show geometrical isomerism ?

Options

A. Potassium tris(oxalato) chromate (III)
B. Pentaaquachlorochromium (III) chloride
C. Aquachlorobis (ethylenediamine) cobalt (II) chloride
D. Potassium aminetrichloroplatinate (II)

Explanation

To determine which of the given complexes will show geometrical isomerism, we need to analyze the coordination complexes based on the types of ligands and their arrangements around the central metal atom. Geometrical isomerism typically occurs in coordination compounds with specific arrangements of ligands, particularly in octahedral and square planar complexes.

### Step-by-Step Solution:

1. **Identify the complexes**:
- Potassium tris(oxalato)chromate(III)
- Pentaquachlorochromium(III) chloride
- Bis(ethylenediamine)(aqua)chlorocobalt(II)
- Potassium amine trichloroplatinate(II)

2. **Analyze each complex for geometrical isomerism**:
- **Potassium tris(oxalato)chromate(III)**: This complex has three identical oxalate ligands (C2O4). Since all ligands are the same, it cannot exhibit cis/trans isomerism. **(No geometrical isomerism)**

- **Pentaquachlorochromium(III) chloride**: This complex has five water ligands and one chloride ligand. Since there are not two different types of ligands that can be arranged differently, it cannot exhibit geometrical isomerism. **(No geometrical isomerism)**

- **Bis(ethylenediamine)(aqua)chlorocobalt(II)**: This complex has two ethylenediamine (en) ligands, one water (H2O) ligand, and one chloride (Cl) ligand. The presence of two different types of ligands (en and Cl) allows for cis and trans arrangements. Therefore, this complex can exhibit geometrical isomerism. **(Yes, it shows geometrical isomerism)**

- **Potassium amine trichloroplatinate(II)**: This complex has three identical chloride ligands and one amine ligand. Since all three chloride ligands are the same, it cannot exhibit geometrical isomerism. **(No geometrical isomerism)**

3. **Conclusion**: Among the given complexes, only the **Bis(ethylenediamine)(aqua)chlorocobalt(II)** complex shows geometrical isomerism.

### Final Answer:
The complex that will show geometrical isomerism is **Bis(ethylenediamine)(aqua)chlorocobalt(II)**.