Question

Leaching method is used to concentrate ores of:
A.Gold
B.Silver
C.Aluminium
D.All of these

Answer 1

To identify the type of ores concentrated by the method of Leaching, we need to first understand what is leaching and or important methods of concentration of ores in metallurgy. Leaching is basically making ore soluble and impurities insoluble in solution.

Complete step by step answer:
There are four main types of concentration of ores:
Hydraulic washing: it concentrates ores which are not chemically attached to its impurities. It is based on gravity for. An upstream of water is run through ore where light impurities get separated from heavy metal ore.
Magnetic separation: it separates ore, which possesses the magnetic property. Ore is converted into fine pieces and is run through the conveyor belt, with a magnetic roller. Ore gets attached to the magnetic roller and gangue gets separated from it.
Froth flotation method: it concentrates Sulphide ores, the ore is converted into powder. And makes suspension using water. Two of the components of it are collectors and froth stabilizers. Collectors stop metals to get wet and stabilizer stabilizes froth formation. Metal gets combined with oil, and gangue gets combined with water. and froth is skimmed off and metal is dried up to acquire pure ore.
Leaching: it concentrates ore if metal particles of ore are soluble in certain solvent and gangue. Now ore is converted into powder and can be treated by a chemical such as $NaOH$. metal particles get dissolved in this chemical and form a solution and gangue remains insoluble.
Leaching is done in case of aluminium, gold and silver. Aluminium is treated with sodium hydroxide and gold and silver which is treated with sodium cyanide.
So, the correct option is $D$ .

Note:
Several ores can be concentrated using only these four methods, all ores depend on different properties, so one needs to know which property ore possesses if ore possesses magnetic property n we will use magnetic separation.