White phosphorus on reaction with concentrated NaOH solution in an inert atmosphere of `CO_(2)`, gives phosphine and compound (X). (X) on acidification with HCl gives compound (Y). The basicity of compound (Y) is:

Options

A. 3
B. 5
C. 2
D. 1

Answer

To solve the problem step by step, we will analyze the reaction of white phosphorus with concentrated NaOH and the subsequent reactions leading to the determination of the basicity of compound Y.

### Step 1: Identify the reaction of white phosphorus with NaOH
White phosphorus (P₄) reacts with concentrated sodium hydroxide (NaOH) in the presence of water (H₂O) to produce phosphine (PH₃) and a compound (X). The reaction can be written as:

\[ P_4 + 4 NaOH + 2 H_2O \rightarrow 2 PH_3 + 2 NaH_2PO_2 \]

Here, NaH₂PO₂ (sodium hypophosphite) is the compound (X).

### Step 2: Acidification of compound (X)
When compound (X), which is NaH₂PO₂, is treated with hydrochloric acid (HCl), it undergoes acidification to yield compound (Y). The reaction can be represented as:

\[ NaH_2PO_2 + HCl \rightarrow H_3PO_2 + NaCl \]

In this reaction, H₃PO₂ (phosphorous acid) is formed as compound (Y).

### Step 3: Determine the structure of compound (Y)
The structure of H₃PO₂ can be drawn as follows:

```
O
||
H - P - OH
|
H
```

### Step 4: Analyze the basicity of compound (Y)
Basicity is defined as the number of ionizable hydrogen ions (H⁺) that a compound can donate. In the case of H₃PO₂, we can see that there is only one ionizable hydrogen atom that can dissociate to release H⁺.

### Conclusion
Since H₃PO₂ has only one ionizable hydrogen ion, its basicity is 1.

### Final Answer
The basicity of compound (Y) is 1.

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