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Question

Name the reagent used in the leaching of gold.


A

Carbon

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B

Iodine

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C

Sodium cyanide

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D

Carbon monoxide

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Solution

The correct option is C

Sodium cyanide


The explanation for the correct option:

Option (C): Sodium cyanide

  • Gold is usually found in low proportions in the form of mined ore. Differentiating gold from other minerals in the ore is essential.
  • Because gold is a soluble mineral, it must be separated from other minerals. As a result, sodium cyanide can be added, forming a complex ion with the gold molecules.4Au(s)Gold+8NaCN(s)Sodiumcyanide+O2(g)Oxygen+2H2O(l)Water4NaAu(CN)2(s)Sodiumgoldcyanide+4NaOH(l)Sodiumhydroxide
  • The ore is crushed and ground. If the gold-bearing ore also contains other metals or sulfide minerals, it will require additional treatment before being leached.
  • Gold is combined with sodium cyanide to create soluble gold.
  • Because gold is soluble after the leaching process, it may move freely through the membrane whereas the remainder of the ore cannot.
  • Hence, it is the correct option.

The explanation for the incorrect options:

Option (A): Carbon

  • Carbon is an abundant element. Diamonds and graphite are examples of pure carbon, although they may also combine with other elements to form molecules.
  • Under normal circumstances, carbon is quite inert.
  • Inks and paints are made from amorphous carbon. It is also utilized in the manufacture of batteries. The lead-in your pencils is made of graphite. It is also required in the process of steel-making.

Option (B): Iodine

  • Iodine is a chemical element with the atomic number 53. Under typical conditions, it exists as a semi-lustrous, non-metallic solid, making it the heaviest of the stable halogens.
  • Iodine is present in two forms i.e. non-radioactive and radioactive forms. Iodine is used to disinfect surfaces and storage containers, as well as in skin cleansers and bandages and for water purification.

Option (D): Carbon monoxide

  • Carbon monoxide is a combustible gas that is colorless, very toxic, odorless, and tasteless. It is less dense than air.
  • Carbon monoxide is an important industrial chemical. It is commonly utilized as a fuel in industrial processes in the form of producer gas or water gas. The gas can also be used as a reducing agent.
  • The gas is also used in the Fischer-Tropsch process, which produces hydrocarbons.

Therefore, Sodium cyanide is used in the leaching of gold.


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