`HCN+H_(2)Orarr[X]+NH_(3), [X]rarr[Y]+H_(2)O` (Unbalanced equations)
[Y] May be prepared by which one of the following methods?

Options

A. By dehydration of Malonic acid with `P_(2)O_(5)`
B. By thermal decomposition of carbon sub - oxide in air.
C. By heating potassium hexacyanoferrate (II) with conc. `H_(2)SO_(4)`
D. By the action of conc. `HNO_(3)` on charcoal.

Answer

To solve the question, we will analyze the given unbalanced equations step by step and determine which method can be used to prepare compound Y.

### Step 1: Analyze the first reaction
The first reaction is:
\[ \text{HCN} + \text{H}_2\text{O} \rightarrow [X] + \text{NH}_3 \]

Here, HCN (hydrogen cyanide) reacts with water to produce compound X and ammonia (NH3).

### Step 2: Identify compound X
When HCN reacts with water, it can form methanoic acid (formic acid), which has the formula HCOOH. Therefore, we can write:
\[ \text{HCN} + 2\text{H}_2\text{O} \rightarrow \text{HCOOH} + \text{NH}_3 \]

### Step 3: Analyze the second reaction
The second reaction is:
\[ [X] \rightarrow [Y] + \text{H}_2\text{O} \]

Substituting X with HCOOH:
\[ \text{HCOOH} \rightarrow [Y] + \text{H}_2\text{O} \]

When methanoic acid (HCOOH) is heated, it can decompose to produce carbon monoxide (CO) and water:
\[ \text{HCOOH} \rightarrow \text{CO} + \text{H}_2\text{O} \]

Thus, Y is identified as CO.

### Step 4: Evaluate the preparation methods for Y
Now we need to evaluate the given methods to see which one can produce CO.

1. **Dehydration of malonic acid with P2O5**:
- Malonic acid (C3H4O4) when dehydrated does not produce CO; it produces carbon suboxide (C3O2).
- **Not suitable.**

2. **Thermal decomposition of carbon suboxide in air**:
- Carbon suboxide (C3O2) decomposes to CO2 and does not yield CO.
- **Not suitable.**

3. **Heating potassium hexacyanoferrate(II) with concentrated H2SO4**:
- This reaction produces CO along with other products:
\[ \text{K}_4\text{Fe(CN)}_6 + 6 \text{H}_2\text{SO}_4 \rightarrow 2 \text{K}_2\text{SO}_4 + \text{FeSO}_4 + 3 \text{(NH}_4)_2\text{SO}_4 + 6 \text{CO} \]
- **Suitable method.**

4. **Action of concentrated HNO3 and charcoal**:
- This reaction produces CO2 and does not yield CO:
\[ \text{C} + 4 \text{HNO}_3 \rightarrow \text{CO}_2 + 4 \text{NO}_2 + 2 \text{H}_2\text{O} \]
- **Not suitable.**

### Conclusion
The only suitable method to prepare Y (CO) is by heating potassium hexacyanoferrate(II) with concentrated H2SO4.

### Final Answer:
Y may be prepared by heating potassium hexacyanoferrate(II) with concentrated H2SO4.

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