The aqueous solution of potassium cyanide is mixed with aqueous solution of `F_e(CN)_2` . The resulting solution will give test for

Options

A. `K^+ and CN^(-)` ions
B. `K^(+) , Fe ^(2+) and CN^(-)` ions
C. `K^(+) and [Fe(CN)_6]^(3-)` ions
D. `K^(+) and [Fe(CN)_6]^(4-)` ions

Answer

To solve the question regarding the reaction between potassium cyanide (KCN) and ferrous cyanide (Fe(CN)₂), we will follow these steps:

### Step 1: Identify the Reactants
We have two reactants:
- Potassium cyanide (KCN), which dissociates in water to give K⁺ and CN⁻ ions.
- Ferrous cyanide (Fe(CN)₂), which dissociates to give Fe²⁺ and CN⁻ ions.

**Hint:** Write down the dissociation of each compound to understand the ions involved.

### Step 2: Write the Reaction
When KCN is mixed with Fe(CN)₂, the cyanide ions (CN⁻) from both compounds can interact with the ferrous ions (Fe²⁺) to form a complex. The reaction can be represented as:
\[ \text{Fe(CN)}_2 + 4 \text{KCN} \rightarrow \text{K}_4[\text{Fe(CN)}_6] \]

This indicates that a coordination complex, potassium ferrocyanide (K₄[Fe(CN)₆]), is formed.

**Hint:** Look for coordination complexes that can form from the ions present in the solution.

### Step 3: Analyze the Resulting Complex
The resulting complex, K₄[Fe(CN)₆], contains:
- 4 potassium ions (K⁺)
- 1 ferrocyanide ion ([Fe(CN)₆]⁴⁻)

This complex is stable and can be tested for the presence of the ferrocyanide ion.

**Hint:** Identify the key components of the complex formed to determine what tests can be conducted.

### Step 4: Determine the Test
The presence of the ferrocyanide ion ([Fe(CN)₆]⁴⁻) can be tested using various methods, such as adding a ferric ion (Fe³⁺) which will produce a blue precipitate known as Prussian blue (ferrous ferricyanide).

**Hint:** Consider common tests for coordination complexes, especially those involving transition metals.

### Conclusion
The resulting solution from mixing potassium cyanide and ferrous cyanide will give a test for the ferrocyanide ion ([Fe(CN)₆]⁴⁻).

**Final Answer:** The resulting solution will give a test for ferrocyanide ion.

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