There are some deposits of nitrated and phosphates in the earth's crust. Nitrates are more soluble in water. Nitrates are difficult to reduce under laboratory conditions but microbes do it easily. Ammonia forms a large number of complexes with transition metal ions. Hybridisation easily explains the ease of sigma donation capability of `NH_3` and `PH_3`. Phosphine is a flammable gas and is prepared from white phosphorous.
White phosphorous on reaction with `NaOH` gives `PH_3` as one of the products. This is a.

Options

A. dimerisation reaction
B. disproportionation reaction
C. condensation reaction
D. precipitation reaction.

Explanation

To determine the type of reaction that occurs when white phosphorus reacts with sodium hydroxide to produce phosphine, we can follow these steps:

### Step 1: Write the Reaction
The reaction between white phosphorus (P₄) and sodium hydroxide (NaOH) can be represented as:
\[ P_4 + 4 NaOH \rightarrow 2 PH_3 + 2 NaH_2PO_2 \]

### Step 2: Identify the Oxidation States
Next, we need to identify the oxidation states of phosphorus in the reactants and products:
- In white phosphorus (P₄), the oxidation state of phosphorus is 0 (elemental form).
- In phosphine (PH₃), the oxidation state of phosphorus is -3.
- In sodium hypophosphite (NaH₂PO₂), we can calculate the oxidation state of phosphorus. Let the oxidation state of phosphorus be \( x \):
\[ Na (+1) + 2H (+1) + 2O (-2) = 0 \implies x + 1 + 2 - 4 = 0 \implies x = +1 \]
Thus, in NaH₂PO₂, the oxidation state of phosphorus is +1.

### Step 3: Analyze the Changes in Oxidation State
Now, we analyze the changes in oxidation states:
- Phosphorus in white phosphorus (0) is reduced to -3 in phosphine (PH₃).
- Phosphorus in white phosphorus (0) is oxidized to +1 in sodium hypophosphite (NaH₂PO₂).

### Step 4: Determine the Type of Reaction
Since the same element (phosphorus) is both oxidized and reduced in this reaction, it qualifies as a disproportionation reaction. In a disproportionation reaction, one species is simultaneously oxidized and reduced.

### Conclusion
Therefore, the reaction of white phosphorus with sodium hydroxide to produce phosphine is an example of a **disproportionation reaction**.

### Final Answer
The answer is: **Disproportionation reaction**.

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