Which of the following reactions can evolve phosphine ?

Options

A. White `P + Ca(OH)_2 rarr`
B. `AlP + H_2 O rarr`
C. `H_3 PO_4 overset (Heat) rarr`
D. `PH_4 I + NaOH rarr`.

Answer

To determine which of the given reactions can evolve phosphine (PH3), we will analyze each option step by step.

### Step 1: Analyze the first reaction
**Reaction:** P4 + Ca(OH)2 → PH3 + CaH2PO2

- White phosphorus (P4) reacts with calcium hydroxide (Ca(OH)2).
- The products include phosphine (PH3) and calcium hydrogen phosphite (CaH2PO2).
- **Conclusion:** This reaction evolves phosphine.

### Step 2: Analyze the second reaction
**Reaction:** AlP + H2O → PH3 + Al(OH)3

- Aluminum phosphide (AlP) reacts with water (H2O).
- The products include phosphine (PH3) and aluminum hydroxide (Al(OH)3).
- **Conclusion:** This reaction also evolves phosphine.

### Step 3: Analyze the third reaction
**Reaction:** H3PO4 (heating) → P2O5

- When phosphoric acid (H3PO4) is heated, it decomposes to form diphosphorus pentoxide (P2O5).
- There are no phosphine (PH3) products formed in this reaction.
- **Conclusion:** This reaction does not evolve phosphine.

### Step 4: Analyze the fourth reaction
**Reaction:** PH4I + NaOH → PH3 + NaI + H2O

- Phosphonium iodide (PH4I) reacts with sodium hydroxide (NaOH).
- The products include phosphine (PH3), sodium iodide (NaI), and water (H2O).
- **Conclusion:** This reaction also evolves phosphine.

### Final Conclusion
The reactions that evolve phosphine are:
1. P4 + Ca(OH)2
2. AlP + H2O
3. PH4I + NaOH

### Summary of Results
- **Reactions that evolve phosphine:** 1, 2, and 4.
- **Reaction that does not evolve phosphine:** 3.