Which of the following phosphorus halide is the best reducing agent?

Options

A. `PCl_(3)`
B. `PF_(3)`
C. `PBr_(3)`
D. `PI_(3)`

Answer

To determine which phosphorus halide is the best reducing agent among the options PCl3, PBr3, and PI3, we can follow these steps:

### Step 1: Understand the Concept of Reducing Agents
A reducing agent is a substance that donates electrons in a chemical reaction and gets oxidized in the process. The strength of a reducing agent can be influenced by the stability of the halide formed after reduction.

### Step 2: Identify the Halides
The halides in question are:
- PCl3 (Phosphorus trichloride)
- PBr3 (Phosphorus tribromide)
- PI3 (Phosphorus triiodide)

### Step 3: Analyze the Trend in Reducing Ability
The reducing ability of phosphorus halides generally increases as we move down the group in the periodic table. This is because larger halogens (like iodine) tend to form weaker bonds with phosphorus compared to smaller halogens (like chlorine). As a result, the bond in PI3 is weaker, making it easier for PI3 to donate electrons.

### Step 4: Compare the Reducing Strength
- PCl3: Chlorine is a smaller halogen, and the bond with phosphorus is stronger, making it a weaker reducing agent.
- PBr3: Bromine is larger than chlorine, so PBr3 has a better reducing ability than PCl3 but is still weaker than PI3.
- PI3: Iodine is the largest halogen, and PI3 has the weakest bond among the three, making it the best reducing agent.

### Conclusion
Based on the trend in reducing ability, PI3 is the best reducing agent among the given phosphorus halides.

**Final Answer:** PI3 is the best reducing agent.

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