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The ferrous ion in a given sample is det...

The ferrous ion in a given sample is detected by the formation of a white precipitate on the addition of a potassium ferrocyanide solution to it. The precipitate has the constitutional formula:

A

`K_(2)Fe^(II)[Fe^(II)(CN)_(6)]`

B

`K_(2)Fe^(III)[Fe(CN)_(6)]`

C

`KF e^(III)[Fe^(II)(CN)_(6)]`

D

`KF e^(II)[Fe^(III)(CN)_(6)]`

Text Solution

AI Generated Solution

The correct Answer is:
To determine the constitutional formula of the white precipitate formed when ferrous ions are treated with potassium ferrocyanide, we can follow these steps: ### Step-by-Step Solution: 1. **Understanding the Reaction**: When potassium ferrocyanide (K₄[Fe(CN)₆]) is added to a solution containing ferrous ions (Fe²⁺), a white precipitate is formed. This indicates that ferrous ions are reacting with the ferrocyanide ions. 2. **Identifying the Oxidation States**: In the potassium ferrocyanide, the iron (Fe) is in the +2 oxidation state. For the precipitate to form correctly, we need to ensure that the iron in the precipitate is also in the +2 oxidation state. 3. **Writing the Formula for the Precipitate**: The general formula for the precipitate formed can be represented as K₂[Fe₂(CN)₆]. This indicates that there are two ferrous ions (Fe²⁺) coordinating with the ferrocyanide ions. 4. **Evaluating the Options**: We need to evaluate the given options to find the one that matches our derived formula: - **Option 1**: K₂Fe₂Fe₂(CN)₆ - This option has all Fe in +2 oxidation state, which is correct. - **Option 2**: K₂Fe₃Fe(CN)₆ - This option has Fe in +3 and +1 oxidation states, which is incorrect. - **Option 3**: KFe₃Fe₂(CN)₆ - This option has Fe in +3 and +2 oxidation states, and it forms a different colored precipitate (Prussian blue), which is incorrect. - **Option 4**: KFe₂Fe₃(CN)₆ - This option has Fe in +2 and +3 oxidation states and forms Turnbull's blue, which is also incorrect. 5. **Conclusion**: Based on the evaluation, the correct constitutional formula of the white precipitate formed when ferrous ions react with potassium ferrocyanide is K₂[Fe₂(CN)₆]. ### Final Answer: The constitutional formula of the white precipitate is **K₂[Fe₂(CN)₆]**.
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