A: dien is bidentate ligand.
R:dien donates two pairs of electron 

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. ) If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question regarding the assertion and reason about the ligand "dien," we will analyze both statements step by step.

### Step 1: Understanding the Assertion
- The assertion states that "dien is a bidentate ligand."
- A bidentate ligand is defined as a ligand that can form two bonds with a metal ion due to the presence of two donor atoms.

### Step 2: Analyzing the Ligand "dien"
- "dien" refers to diethylenetriamine, which has the structure: NH2CH2CH2NHCH2CH2NH2.
- This ligand contains three nitrogen atoms, each of which has a lone pair of electrons that can be donated to a metal ion.

### Step 3: Evaluating the Reason
- The reason states that "dien donates two pairs of electrons."
- Since dien has three nitrogen atoms, it can donate three pairs of electrons (one pair from each nitrogen atom). Therefore, this statement is incorrect in the context of dien being a bidentate ligand.

### Step 4: Conclusion
- The assertion is true because dien can act as a bidentate ligand, but the reason is false because dien donates three pairs of electrons, not two.
- Therefore, the correct conclusion is that the assertion is true, but the reason is false.

### Final Answer:
- Assertion (A) is true, and Reason (R) is false.

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