In the process of extraction of gold, the following reaction takes places: Roasted gold ore +CN−+O2+2H2O→[X]+OH− [X]+Zn→[Y]+Au
Identify the compounds [X] and [Y].
A
[X]=[Au(CN)4]3−,[Y]=[Zn(CN)4]2−
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B
[X]=[Au(CN)2]−,[Y]=[Zn(CN)4]2−
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C
[X]=[Au(CN)4],[Y]=[Zn(CN)6]2−
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D
[X]=[Au(CN)2]−,[Y]=[Zn(CN)6]4−
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Solution
The correct option is B[X]=[Au(CN)2]−,[Y]=[Zn(CN)4]2− In the metallurgy of silver and that of gold, the respective metal is leached with a dilute solution of NaCN or KCN in the presence of air (for O2) from which the metal is obtained later by replacement: 4Roasted gold ore +8CN−+O2(g)+2H2O(aq)→[Au(CN)2]−(aq)+4OH−(aq) 2[Au(CN)2]−(aq)+Zn(s)→[Zn(CN)4]2−(aq)+2Au(s)
Hence, [X]=[Au(CN)2]−and [Y]=[Zn(CN)4]2−
Hence option (a) is correct.