Extraction of Metals - Result Question 14
####14. The electrolytes usually used in the electroplating of gold and silver, respectively, are
(a) $\left[Au(OH) _4\right]^{-}$and $\left[Ag(OH) _2\right]^{-}$
(2019 Main, 10 Jan II)
(b) $\left[Au\left(NH _3\right) _2\right]^{+}$and $\left[Ag(CN) _2\right]^{-}$
(c) $\left[Au(CN) _2\right]^{-}$and $\left[Ag(CN) _2\right]^{-}$
(d) $\left[Au(CN) _2\right]^{-}$and $\left[AgCl _2\right]^{-}$
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Solution:
- Electroplating is a process of coating one metal or metal object with a very thin layer of another metal typically applying a direct electric current.
Electrolytes used in the electroplating of gold and silver are given in the table below:
| Process | Article to be plated out acts as cathode |
Pure metal block acts an anode by which electroplating will be done |
Electrolyte (aqueous solution) |
|
|---|---|---|---|---|
| (a) | Gold plating |
Article | $Au(s)$ | $I$ $Na\left[Au(CN) _2\right]$ (Sodium auro-cyanide) |
| (b) | Silver plating |
Article | $\operatorname{Ag}(s)$ | $I$ $Na\left[Ag(CN) _2\right]$ (Sodium argento cyanide) |
