`Fe^(2+) and Fe^(3+)` can be distinguished by

Options

A. `K_(3)[Fe(CN)_(6)]`
B. `K_(4)[Fe(CN)_(6)]`
C. `KSCN`
D. All are correct

Answer

To distinguish between Fe²⁺ and Fe³⁺ ions, we can perform a series of reactions with specific reagents. Here’s a step-by-step solution:

### Step 1: Reaction with K₃[Fe(CN)₆]
- **Fe²⁺ Reaction**: When Fe²⁺ reacts with potassium ferricyanide (K₃[Fe(CN)₆]), it forms a blue precipitate known as Turnbull's blue (KFe[Fe(CN)₆]).
- **Fe³⁺ Reaction**: When Fe³⁺ reacts with the same reagent, it forms a brown precipitate (Fe[Fe(CN)₆]).

### Step 2: Reaction with K₄[Fe(CN)₆]
- **Fe²⁺ Reaction**: When Fe²⁺ reacts with potassium ferrocyanide (K₄[Fe(CN)₆]), it produces a white precipitate (K₂[Fe(Fe(CN)₆)]).
- **Fe³⁺ Reaction**: When Fe³⁺ reacts with the same reagent, it produces a blue precipitate known as Prussian blue (KFe[Fe(CN)₆]).

### Step 3: Reaction with KSCN
- **Fe²⁺ Reaction**: There is no significant reaction between Fe²⁺ and potassium thiocyanate (KSCN), meaning no precipitate is formed.
- **Fe³⁺ Reaction**: When Fe³⁺ reacts with KSCN, it forms a blood-red colored complex (Fe(SCN)³⁺).

### Conclusion
By observing the color and type of precipitate formed in these reactions, we can distinguish between Fe²⁺ and Fe³⁺ ions. The distinct colors of the precipitates and the formation of a complex with KSCN for Fe³⁺ only help in identifying the oxidation states of iron.

### Final Answer
Fe²⁺ and Fe³⁺ can be distinguished by their reactions with K₃[Fe(CN)₆], K₄[Fe(CN)₆], and KSCN, which produce different colored precipitates and complexes.

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