The statement which is not correct , is

Options

A. Chlorophyll is responsible for the synthesis of carbohydrates in plants .
B. The compound formed by the addition of oxygen to haemoglobin is called oxyhaemoglobin
C. Acetyl salicylic acid is known as aspirin .
D. the metal ion present in vitamin `B_(12)` is `Mg^(2+)`

Explanation

To solve the question, we need to analyze each statement provided and identify which one is incorrect. Let's go through the statements one by one:

1. **Chlorophyll is responsible for the synthesis of carbohydrates in plants.**
- This statement is correct. Chlorophyll is a green pigment found in plants that plays a crucial role in photosynthesis, the process by which plants synthesize carbohydrates (like glucose) using sunlight, carbon dioxide, and water.

2. **The compound formed by the addition of oxygen to hemoglobin is called oxyhemoglobin.**
- This statement is also correct. When oxygen binds to hemoglobin in red blood cells, it forms a complex known as oxyhemoglobin, which is essential for transporting oxygen throughout the body.

3. **Acetylsalicylic acid is called aspirin.**
- This statement is correct as well. Acetylsalicylic acid is the chemical name for aspirin, which is commonly used as an analgesic (pain reliever) and anti-inflammatory medication.

4. **The metal ion present in vitamin B12 is Mg2+.**
- This statement is incorrect. The metal ion present in vitamin B12 (also known as cobalamin) is cobalt (Co), not magnesium (Mg). Therefore, this statement is false.

### Conclusion:
The statement that is not correct is the fourth one: "The metal ion present in vitamin B12 is Mg2+."

### Final Answer:
The incorrect statement is: **The metal ion present in vitamin B12 is Mg2+.**

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