Question

How many metals are commercially extracted by hydrometallurgy from the given metals?
(Ag, Mn, In, Cr, Pb, Au)

Answer 1

Hint: Hydrometallurgy is a branch of metallurgy in which metals are extracted by treating the ores with aqueous solutions. It involves the electrolysis process for the recovery of metals. So all the metals cannot be extracted through it. Metals that can be easily reduced are only extracted.

Complete step by step answer:
-Metal compounds found in nature are called minerals. Minerals from which we can extract metals conveniently as well as economically are called ores. It contains impurities which are called gangue.
-Extraction of metals from ores is called metallurgy. Metals are extracted from the earth’s surface and so along with the metals, certain impurities also appear with it which needs to be removed in order to increase the efficiency of the metals.

-Hydrometallurgy involves the processes of leaching, concentration and purification of solution and metal recovery process. The metal is recovered by electrolysis where reduction of the metal ore is done in order to get the pure metal.
-Reaction takes place at the electrodes. Electrode where oxidation occurs is called anode and electrode where reduction occurs is called cathode. These processes are governed by electrochemical series. The top elements behave as reducing agents and as we go down, the strength of the oxidizing agents increase.

-So basically the electrochemical series governs the metals that can be obtained by the process of hydrometallurgy. More electropositive metals can reduce the less electropositive metals from their ores.
- Electropositivity is the tendency of an atom to lose the electrons and achieve the octet configuration of the nearest noble gas. Along the period, electronegativity increases. So electropositivity decreases. Down the group, electronegativity decreases and so the electropositivity increases.
-Thus from the given options we can see that Au and Cr are poor reducing agents than the other metals. So they get reduced during the electrolysis process and are obtained as pure metals while the other metals reduce them and appear as the metal salts.
Therefore the answer to this question is ‘two metals’.

Note: If there are metals which have variable valencies like copper and iron, they have different strengths of their reducing capabilities. Example - Copper is a better reducing agent when it is in (II) form rather than (I) form. So always take care of such metals while observing the reducing power.