For the given aqueous reactions, which of the statement(s) is (are) true ?
(A)The first reaction is a recox reaction.✓ Correct
(B)White precipitate is Zn3[Fe(CN)6]2.
(C)Addition of filtrate to starch solution gives blue colour.✓ Correct
(D)White precipitate is soluble in NaOH solution.✓ Correct
Answer: (A), (C), (D)
Solution
The first reaction is K₃[Fe(CN)₆] + excess KI → K₄[Fe(CN)₆] + I₃⁻, a redox reaction where Fe³⁺ is reduced to Fe²⁺ and I⁻ is oxidized to I₃⁻, so (A) is correct. The filtrate contains I₃⁻ which gives blue color with starch, so (C) is correct. The white precipitate is K₂Zn₃[Fe(CN)₆]₂ which dissolves in NaOH to form Na₂[Zn(OH)₄], so (D) is correct. The formula in (B) is incorrect. The answer is (A), (C), (D).
JEE Advanced · 2012 · 08 Apr 2012 · Paper 2 · One or more correct options
