Leaching of gold with dilute aqueous solution of NaCN in presence of oxygen gives complex [A], which on reaction with zinc forms the elemental gold and another complex [B]. [A] and [B], respectively are :-

Question

Leaching of gold with dilute aqueous solution of NaCN in presence of oxygen gives complex [A], which on reaction with zinc forms the elemental gold and another complex [B]. [A] and [B], respectively are :- (A) [ Au ( CN )4]-and [ Zn ( CN )2( OH )2]2- (B) [ Au ( CN )2]-and [ Zn ( OH )4]2- (C) [ Au ( CN )2]-and [ Zn ( CN )4]2- (D) [ Au ( CN )4]2- and [ Zn ( CN )6]4-

Tardigrade Admin · Accepted Answer

Au + NaCN arrow Na [ Au ( CN )2] Zn + Na [ Au ( CN )2] arrow Na 2[ Zn ( CN )4]+ Au

Q. Leaching of gold with dilute aqueous solution of $N a CN$ in presence of oxygen gives complex $[A]$ , which on reaction with zinc forms the elemental gold and another complex $[B] . [A]$ and $[B]$ , respectively are :-

$[A u (CN)_{4}]^{-}$ and $[Z n (CN)_{2} (O H)_{2}]^{2 -}$

$[A u (CN)_{2}]^{-}$ and $[Z n (O H)_{4}]^{2 -}$

$[A u (CN)_{2}]^{-}$ and $[Z n (CN)_{4}]^{2 -}$

$[A u (CN)_{4}]^{2 -}$ and $[Z n (CN)_{6}]^{4 -}$

$A u + N a CN \to N a [A u (CN)_{2}]$
$Z n + N a [A u (CN)_{2}] \to N a_{2} [Z n (CN)_{4}] + A u$

Q. Leaching of gold with dilute aqueous solution of NaCN in presence of oxygen gives complex [A], which on reaction with zinc forms the elemental gold and another complex [B].[A] and [B], respectively are :-

[Au(CN)4​]−and [Zn(CN)2​(OH)2​]2−

[Au(CN)2​]−and [Zn(OH)4​]2−

[Au(CN)2​]−and [Zn(CN)4​]2−

[Au(CN)4​]2− and [Zn(CN)6​]4−