Verified Solution • 2025–26 Session moderate

QJEEM22Chd8bf: JEE Main 2022 Chemistry - Class 12 JEEM22Chd8bf Solution: Statement I : Leaching of gold with cyanide ion in absence of…

Statement I : Leaching of gold with cyanide ion in absence of air / O2 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.

Multiple Choice Options

  • 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.

Step-by-Step Verified Solution

Leaching of gold with cyanide ion is done in presence of air/O2 leading to cyano complex [Au(CN)2]– where Au is in +1 oxidation state.

4Au(s) + 8CN–(aq) + 2H2O(aq) + O2(g) ⟶4[Au(CN)2]aq−+4OH−\longrightarrow 4\left[\mathrm{Au}(\mathrm{CN})_{2}\right]_{\mathrm{aq}}^{-}+4 \mathrm{OH}^{-}

2[Au(CN)2](aq)−amp;+Zn(s)amp;⟶[Zn(CN)4](aq)2−+2Au(s)\begin{aligned} 2\left[\mathrm{Au}(\mathrm{CN})_{2}\right]_{(\mathrm{aq})}^{-} &+\mathrm{Zn}(\mathrm{s}) \\ & \longrightarrow\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]_{(\mathrm{aq})}^{2-}+2 \mathrm{Au}(\mathrm{s}) \end{aligned}

Zinc is oxidised from (0) to +2 oxidation state during displacement reaction carried out for gold extraction.

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