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NEET levelSingle correct optionDifficulty 1 of 3mt119

After leaching a gold ore with aqueous $NaCN$ and air, gold is recovered from the solution of $Na [Au (CN) X_{2}]$ by adding

Acarbon monoxide
Bdilute hydrochloric acid
Czinc dust
Dexcess $NaCN$ solution

Answer: C

Zinc is a stronger reducing agent than gold and displaces it:

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

. Gold is obtained as a precipitate.

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