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MCQEasyJEE 2023Ligands & Coordination Number

JEE Chemistry 2023 Question with Solution

The complex that dissolves in water is:

  • A

    Fe₄[Fe(CN)₆]₃, Prussian Blue insoluble

  • B

    Fe₆[Fe(CN)₆]₃

  • C

    K₄[Co(CO)₆]

  • D

    (NH₄)₆[As(MoO₄)₆]

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: The question asks which complex dissolves in water.

Find: The water-soluble complex.

The solution states that Fe₄[Fe(CN)₆]₃ is Prussian Blue and is insoluble in water. It also states that compounds like K₄[Co(CO)₆] are soluble due to the ionic nature of the complex.

However, the same source then concludes, "The correct answer is (1)," which contradicts its own explanation and also contradicts the wording of the question.

Based on the explanation provided in the solution, the dissolving complex is K₄[Co(CO)₆].

Therefore, the most defensible correct option is C.

Common mistakes

  • Selecting Prussian Blue because it is a famous complex is incorrect. The solution text itself identifies Fe₄[Fe(CN)₆]₃ as insoluble in water, so it cannot answer a question asking for the complex that dissolves in water.

  • Trusting the final marked option without checking the explanation can lead to error. Here, the written explanation supports K₄[Co(CO)₆] as soluble, so the reasoning must be preferred over the contradictory option label.

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