`K_(4)[Fe(CN)_(6)]+M^(x+)(aq.)to underset("Coloured precipitate")(M_(4)[Fe(CN)_(6)]_(x)darr)`
Which of the following cation does not respond to the above reaction?

Options

A. `Cu^(2+)(aq.)`
B. `Fe^(3+)(aq.)`
C. `Zn^(2+)(aq.)`
D. None of these

Explanation

To solve the question, we need to analyze the reaction involving potassium ferricyanide, \( K_4[Fe(CN)_6] \), and various cations \( M^{x+} \). The goal is to identify which cation does not produce a colored precipitate when reacting with potassium ferricyanide.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in the reaction are \( K_4[Fe(CN)_6] \) (potassium ferricyanide) and a cation \( M^{x+} \) in aqueous solution.

2. **Understand the Reaction**: The reaction can be represented as:
\[ K_4[Fe(CN)_6] + M^{x+} \rightarrow M_4[Fe(CN)_6] + X \]
This reaction is expected to form a colored precipitate of the complex \( M_4[Fe(CN)_6] \).

3. **Analyze Different Cations**:
- **Cation 1: \( Cu^{2+} \)**: When \( K_4[Fe(CN)_6] \) reacts with \( Cu^{2+} \), it forms a red-brown colored precipitate \( Cu_2[Fe(CN)_6] \). This indicates that \( Cu^{2+} \) responds to the reaction.

- **Cation 2: \( Fe^{3+} \)**: The reaction of \( K_4[Fe(CN)_6] \) with \( Fe^{3+} \) produces a dark blue precipitate known as Prussian blue, \( KFe[Fe(CN)_6] \). This also indicates a response to the reaction.

- **Cation 3: \( Zn^{2+} \)**: When \( K_4[Fe(CN)_6] \) reacts with \( Zn^{2+} \), it forms a white precipitate \( Zn_2[Fe(CN)_6] \). Since this precipitate is not colored, \( Zn^{2+} \) does not respond to the reaction in the context of producing a colored precipitate.

4. **Conclusion**: Based on the analysis, the cation that does not produce a colored precipitate when reacting with potassium ferricyanide is \( Zn^{2+} \).

### Final Answer:
The cation that does not respond to the above reaction is \( Zn^{2+} \).

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