When `HNO_(3)` is added to sodium ferrocyanide, which of the following observation is observed ?

Options

A. `NaFe[Fe(CN)_(6)]` is produced.
B. `Fe_(4)[Fe(CN)_(6)]_(3)` is formed.
C. `Fe_(3)[Fe(CN)_(6)]_(2)` is formed.
D. `Na_(2)[Fe(CN)_(5)(NO)^(+)]^(2-)` is formed.

Explanation

To solve the question regarding the observation when HNO₃ is added to sodium ferrocyanide, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this case are sodium ferrocyanide (Na₄[Fe(CN)₆]) and nitric acid (HNO₃).

2. **Understand the Reaction**:
- When HNO₃ is added to sodium ferrocyanide, a chemical reaction occurs. The nitric acid can act as an oxidizing agent.

3. **Write the Chemical Equation**:
- The reaction can be represented as follows:
\[ \text{Na}_4[\text{Fe(CN)}_6] + \text{HNO}_3 \rightarrow \text{Na}_2[\text{Fe(CN)}_5\text{NO}] + \text{NH}_4^+ + \text{CO}_2 \]
- In this reaction, sodium ferrocyanide reacts with nitric acid to form a new complex and other products.

4. **Identify the Products**:
- The main product formed is sodium nitroferrocyanide, which can be represented as Na₂[Fe(CN)₅NO]²⁻.
- Additionally, ammonium ions (NH₄⁺) and carbon dioxide (CO₂) are also produced.

5. **Observation**:
- The formation of a new colored complex (often a deep blue or greenish solution) is typically observed when sodium ferrocyanide reacts with nitric acid.

6. **Conclusion**:
- The correct observation when HNO₃ is added to sodium ferrocyanide is that sodium nitroferrocyanide (Na₂[Fe(CN)₅NO]²⁻) is formed, which indicates a successful reaction.

### Final Answer:
When HNO₃ is added to sodium ferrocyanide, the observation is that sodium nitroferrocyanide (Na₂[Fe(CN)₅NO]²⁻) is formed.

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