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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3mt162

Which statements about extraction of silver by the cyanide process are correct?

Adissolved oxygen oxidises silver (or helps oxidise the sulphide) during leaching
Bone mole of zinc displaces two moles of silver from $Na [Ag (CN) X_{2}]$
Cleaching of argentite does not need air because $Na X_{2} S$ formed is stable and does not interfere
Dthe soluble product contains a linear complex ion $[Ag (CN) X_{2}] X^{-}$

Answer: A, B, D

Air oxidises silver in native ores and removes sulphide from argentite leaching; the complex is

[Ag (CN) X_{2}] X^{-}

; and

2 Na [Ag (CN) X_{2}] + Zn Na X_{2} [Zn (CN) X_{4}] + 2 Ag

. Sulphide ion does interfere by reversing the reaction, so air is needed.

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