`Cu^(-2)(aq)+K_(4)[Fe(CN)_(6)](aq)rarr underset((ppt))X`
Colour of precipitate (X) is

Options

A. green
B. blue
C. white
D. reddish - brown

Explanation

To determine the color of the precipitate formed in the reaction between copper(II) ions and potassium ferrocyanide, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in the equation are \( \text{Cu}^{2+}(aq) \) (copper(II) ions) and \( \text{K}_4[\text{Fe(CN)}_6](aq) \) (potassium ferrocyanide).

2. **Write the Reaction**:
- When copper(II) ions react with potassium ferrocyanide, the reaction can be represented as:
\[ \text{Cu}^{2+}(aq) + \text{K}_4[\text{Fe(CN)}_6](aq) \rightarrow \text{Cu}_2[\text{Fe(CN)}_6](s) + 2 \text{K}^+(aq) \]
- Here, \( \text{Cu}_2[\text{Fe(CN)}_6] \) is the precipitate formed.

3. **Identify the Precipitate**:
- The precipitate formed is \( \text{Cu}_2[\text{Fe(CN)}_6] \), known as copper(II) ferrocyanide.

4. **Determine the Color of the Precipitate**:
- The color of the precipitate \( \text{Cu}_2[\text{Fe(CN)}_6] \) is known to be reddish-brown.

5. **Conclusion**:
- Therefore, the color of the precipitate \( X \) is reddish-brown.

### Final Answer:
The color of precipitate \( X \) is **reddish-brown**.

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