JEE Main · 2022 · 27 Jun 2022 · Shift 2 · General Principles and Processes of Isolation of Metals

Statement I: Leaching of gold with cyanide ion in absence of air /

O_{2}

leads to cyano complex of

Au (III)

.

Statement II : Zinc is oxidized during the displacement reaction carried out for gold extraction.

In the light of the above statements, choose the correct answer from the options given below.

(A)Both Statement I and Statement II are correct
(B)Both Statement I and Statement II are incorrect
(C)Statement I is correct but Statement II is incorrect
(D)Statement I is incorrect but Statement II is correct✓ Correct

Answer: (D)

Solution

Statement I is incorrect because leaching of gold with cyanide in the presence of air/oxygen forms a cyano complex of Au(I), not Au(III):

4 Au + 8 CN^{-} + O_{2} + 2 H_{2} O \to 4 [Au (CN)_{2}]^{-} + 4 OH^{-}

. Statement II is correct because zinc is oxidized during the displacement reaction:

2 [Au (CN)_{2}]^{-} + Zn \to [Zn (CN)_{4}]^{2 -} + 2 Au

JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Single correct option

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JEE Main · 2022 · 27 Jun 2022 · Shift 2 · General Principles and Processes of Isolation of Metals

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