Question

Select the correct statements.
This question has multiple correct options.
(a) In hydrometallurgy, Zn is used as an oxidizing agent in the purification of Ag from ${{[\text {Ag (CN} {{\text {)}} _ {2}}]} ^ {-}} $
(b) When pine oil or eucalyptus oil is added into the water, it lowers down the surface tension by which froth is formed.
(c) Sodium ethyl xanthate is used as a collector.
(d) Basic copper carbonate or $\text {PBS}{{\text{O}} _ {4}} $is concentrated by froth floatation method by using an activator.

Answer 1

Hint: In hydrometallurgy Zn, undergoes oxidation i.e. Involves the loss of electrons and in froth floatation method, we know that it is the method commonly used for the concentration of sulphide ores. Now answer the above statements.

Complete step by step answer:
To find the answer of the above statements, we need to check all the options given in the statement. starting with the option (a)
Option(a): by the term hydrometallurgy we mean, the process of the extraction of the metals from their ores by using the aqueous solutions (i.e. in which water is the solvent). In the hydrometallurgy, the Zn is used as a reducing agent (i.e. which loses electrons) and not as an oxidizing agent (i.e. Gains electrons). Its reaction is as follows:
                           $\text{A}{{\text{g}}_{2}}\text{S+4NaCN }\to \text{2Na }\!\![\!\!\text{ Ag(CN}{{\text{)}}_{2}}\text{ }\!\!]\!\!\text{ +N}{{\text{a}}_{2}}\text{S}$
Silver is obtained by reaction with Zn:
                                    $\text{2Na }\!\![\!\!\text{ Ag(CN}{{\text{)}}_{2}}\text{ }\!\!]\!\!\text{ +Zn }\to \text{N}{{\text{a}}_{2}}\text{ }\!\![\!\!\text{ Zn(CN}{{\text{)}}_{2}}\text{ }\!\!]\!\!\text{ +2Ag}$

thus the option(a) is incorrect.
option (b) and (c): Froth flotation is a technique which is commonly used in the mining industry and in this method, materials are separated on the basis of their hydrophobic (means they are water repelling) and hydrophilic (water loving) nature and is most commonly used method for the separation of sulphide ores. In this, the impurities are removed from the mineral ore and the pure minerals are extracted from it. It is based on the principle of the difference in the wetting properties(the ability of the solute particles to get dissolve in the water ) of the ore and gangue particles and in this, ore is wetted by oil( pine oil)(hydrophobic in nature) and gangue particles (i.e. the impurities present in the ore) are wetted by water( hydrophilic in nature).
In this method, first of all the ore is crushed into small pieces and after that it is mixed with the collector i.e. pine oil ( the collectors enhances the non-wettability of ores i.e. it prevents the ore to not to dissolve in the solvent, the water )and a slurry is formed which is then it is put into the water containing container and a mixture is formed of ore, oil and water. And the impurities present in it and the pine oil added into the water, it lowers down the surface tension by which froth is formed.
The ore particles coated with the pine oil being lighter in nature and are adsorbed on potassium or sodium ethyl xanthate that act as a collector (are the materials which are used to adsorb the materials particles on the surface) and come at the surface along with the froth. The gangue particles being heavier in nature settles down in the water. Some stabilizers like aniline, cresols etc. are added to the froth to maintain the froth for some time over the water surface and after that, the ore along with the froth is taken out of the container and the gangue particles settled down in water are left behind. After that, the froth is dried and the ore is collected from it and is now free of impurities.
 called friends of collectors. They are the easily ionizable soluble salts which react with the mineral surface.

Note: Don’t get confused in the oxidizing and reducing agents. The one which loses electrons undergoes oxidation and acts as a reducing agent. On the other hand, the one which gains electrons undergoes reduction and acts as an oxidizing agent.