The correct reaction involved in the leaching of gold with dilute solution of NaCN is:

4 A u + 8 C N^{-} + 2 H_{2} O + O_{2} (a i r) \to 4 [A u (C N)_{2}]^{-} + 4 O H^{-}

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A u + 2 C N^{-} \to Z n [(C N)_{2}]^{-}

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Z n + 2 C N^{-} \to Z n [(C N)_{2}]^{-}

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Z n + 4 C N^{-} \to Z n [(C N)_{4}]^{2 -}

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Solution

The correct option is A $4 A u + 8 C N^{-} + 2 H_{2} O + O_{2} (a i r) \to 4 [A u (C N)_{2}]^{-} + 4 O H^{-}$
In extraction of gold:
$4 A u + 8 C N^{-} + 2 H_{2} O + O_{2} (a i r) \to 4 [A u (C N)_{2}]^{-} + 4 O H^{-}$
and
$2 [A u (C N)_{2}]^{-} + Z n \to [Z n (C N)_{4}]^{2 -} + 2 A u$

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Similar questions

4 A u + 8 C N^{-} + 2 H_{2} O + O_{2} \to 4 [A u (C N)_{2}]^{-} + 4 O H^{-}

2 [A u (C N)_{2}]^{-} + Z n \to 2 A u + [Z n (C N)_{4}]^{2 -}

Z n \to Z n^{2 +} + 2 e^{-}; E = + 0.76 V

A u \to A u^{3 +} + 3 e^{-}; E = - 1.42 V

Z n^{2 +}

C N^{-}

A u

(K_{f})

Z n^{2 +} (a q) + 4 O H^{-} (a q) ⇌ Z n (O H)_{4}^{2 -} (a q)

p \times 10^{q},

Z n^{2 +} (a q) + 2 e^{-} \to Z n (s); E^{0} = - 0.76 V

Z n (O H)_{4}^{2 -} (a q) + 2 e^{-} \to Z n (s) + 4 O H^{-} (a q); E^{0} = - 1.36 V

2.303 \frac{R T}{F} = 0.06

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