Which of the following statement is incorrect regarding `Fe^(2+) and Fe^(3+)` cations?

Options

A. `Fe^(3+)` gives brown colour solution with potassium ferricyanide
B. `Fe^(2+)` gives blue precipitate with potassium ferricyanide
C. `Fe^(3+)` gives red colour solution with potassium thiocyanate
D. `Fe^(2+)` gives brown colour with ammonium thiocyanate

Explanation

To determine which statement is incorrect regarding the cations Fe²⁺ and Fe³⁺, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Option 1: Fe³⁺ gives a brown color solution with potassium ferricyanide.**
- When Fe³⁺ reacts with potassium ferricyanide (K₃[Fe(CN)₆]), it forms a complex known as ferric ferrocyanide, which is a brown color solution.
- **Conclusion:** This statement is correct.

2. **Option 2: Fe²⁺ gives a blue precipitate with potassium ferricyanide.**
- When Fe²⁺ reacts with potassium ferricyanide, it forms a complex known as Turnbull's blue, which is a blue precipitate.
- **Conclusion:** This statement is correct.

3. **Option 3: Fe³⁺ gives a red color solution with potassium thiocyanate.**
- When Fe³⁺ reacts with potassium thiocyanate (KSCN), it forms a complex known as ferric thiocyanate, which is a red color solution.
- **Conclusion:** This statement is correct.

4. **Option 4: Fe²⁺ gives a brown color with ammonium thiocyanate.**
- When Fe²⁺ is mixed with ammonium thiocyanate (NH₄SCN), no significant reaction occurs, and thus no color change or brown color is observed.
- **Conclusion:** This statement is incorrect.

### Final Answer:
The incorrect statement regarding Fe²⁺ and Fe³⁺ cations is **Option 4: Fe²⁺ gives a brown color with ammonium thiocyanate.**

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