Explore topic-wise InterviewSolutions in Current Affairs.

This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.

1.	Why is the extraction of copper form pyries more difficult then that from its oxide ore through reduction?
Answer» The extraction of copper from pyrites is more difficult than that from its oxide ore through reduction. Explanation : Pyrites `(Cu_(2)S)` cannot be reduced by carbon (or) hydrogent because the standard free energy of formation `(DeltaG^(@))` of `Cu_(2)S`is greater then those of `CS_(2)` and `H_(2)S`. `{:(2Cu_(2)S+Crarr4Cu+CS_(2)),(Cu_(2)S+H_(2)rarrCu+H_(2)S):}}" Not feasible"` `rarr` The `DeltaG^(@)` of copper oxide is less than that of `CO_(2)`. `therefore`The sulphide ore is first converted to oxide by roasting and then reduced. `2Cu_(2)S+3O_(2)underset("heat")overset("Roasting")rarr2Cu_(2)O+2SO_(2)` `2Cu_(2)O+Crarr4Cu+CO_(2)["feasible"]`.

2.	How is leaching carried out in the case of low grade copper ores?
Answer» In case of low grade of copper, hydrometallurgy technuque is used extraction . Here leaching process can be done by using acids (or) bacteria. The solution cantainig` Cu^(+2)` is treated with scrap iron (or) `H_(2)`. `Cu_((aq))^(2+)+H_(2_((g)))rarrCu_((S))+2H_((aq))^(+)`

3.	At a site, low grade copper ores are avilable and Zinc and iron scraps are also avilable . Which of the two scraps would be more suitable for reducing the leached copper ore and why?
Answer» Zinc being above iron in the electrochemical series (more reactive metal is zinc) ,the reduction will be faster in case zinc scraps are used. But zinc is costlier metal than iron. So using iron scraps will be advisable and advantageous.

4.	Copper can be extracted by hydrometallurgy but not Zinc -explain.
Answer» Copper can be extracted by hydrometallurgy but not zinc. Explanation : `rarr E^(0)` value of `Zn^(+2)//Zn= -0.762V` is less than that of `E^(0)` value of `Cu^(+2)//Cu=0.337V.` `rarr` from the above data zinc is a stronger reducing agent and can easily displace the `Cu^(+2)`ions present in the complex. `underset(" Soluble complex")([Cu(CN)_(2)])+Znrarr([Zn(CN)_(2)])+underset("precipitate")(Cu)` Zinc can be isolated by hydrometallurgy only when stronger reducing agents than zinc are present. So zinc cannot be extracted by hydrometallurgy.

5.	Write any two ores with formulae of the following metals: (a) Aluminium (b) Zinc (c) Iron (d) copper
Answer» `{:("a) Ores of Aluminium",:,"Bauxite "-Al_(2)O_(3).2H_(2)O),(,,"Cryolite "-Na_(3)AlF_(6)),("b) Ores of Zinc",:,"Zinc blende "-Zns),(,,"Calamine "-ZnCO_(3)),("c) Ores of Iron" ,:,"Haematite "-Fe_(2)O_(3)),(,,"Magnetite "-Fe_(2)O_(4)),("d) Ores of copper",:,"Copper pyrites "-CuFeS_(2)),(,,"Copper glance "-Cu_(2)S):}`

6.	Give the uses of a) cast iron b) wrought iron c) Nickel steel d) Stainless steel
Answer» a)Uses of cast iron : `rarr` cast iron is used for casting stoves, raiway sleepers ,gutter pipes , toys etc. `rarr` it is used in manufacturing of wrought iron and steel. `rarr` uses of wrought iron : b) `rarr` wrought iron is used in making anchors, wires. `rarr` wrought iron is used in making chains and agricultural implements. c) uses of stainless steel : `rarr` Nickel steel is used for making cables , automobiles and aeroplane parts. `rarr` Nickel steel is used for marking pendulum , measuring tapes , chrome steel for cutting tools and crashing machines. d) uses of stainless steel : `rarr` stainless steel is used in manufacturing of cycles , automobiles. `rarr` stainless steel is used in manufacturing of utensils,pens etc.

7.	Between C and CO, Which is a better reducing agent for ZnO?
Answer» Case-I : [Coke as reducing agent] `ZnO+CrarrZn+CO,DeltaG^(@)` becomes lesser as the T is more then 1120K. Case =II [CO as reducing agent] `ZnO+CO_(2)rarrZN+CO,DeltaG^(@)` becomes lesser when the T is more than 1323K. `rarr` The value of `DeltaG^(@)` is negative for a raction to occur. `rarr` In the equation (1) `DeltaG^(@)` becomes negative at low temperture-so equation (1) is feasible i.r. C is a better reducing agent for ZnO.s

8.	Suggest a condition under which magnesium could reduce alumina.
Answer» The two equations are : a) `(4)/(3)Al+O_(2)rarr(2)/(3)Al_(2)O_(3)" b) "2Mg+O_(2)rarr2MgO` At the point of intersection of the `Al_(2)O_(3)` and MgO curves (marked 'A' in Ellingham diagram), the `DeltaG^(Theta)` becomes ZERO for the reaction : `(2)/(3)Al_(2)O_(3)+2Mg rarr 2MgO +(4)/(3)Al` Below that point magnesium can reduce alumina.

9.	The Value of `DeltaG^(@)` for the formation of `Cr_(2)O_(3)` is `-"540KJ mol"^(-1)` and that of `Al_(2)O_(3)` is `-827"KJ mol"^(-1)`. Is the reduction of `Cr_(2)O_(3)` possible with Al ?
Answer» From the given data the following are the thermo chemical equations . `(4)/(3)Cr_((S))+O_(2_((g)))rarr(2)/(3)Cr_(2)O_(3(s)),DeltaG^(@)-540KJ" ...(1)"` `(4)/(3)Cr_(2)O_(3_((s)))+O_(2_((g)))rarr(2)/(3)Al_(2)O_(3_((s))),DeltaG^(@)-827KJ" ...(2)"` Equation (1)-Equation (2) `(2)/(3)Cr_(2)O_(3_((s)))+(4)/(3)Al_(s)rarr(2)/(3)Al_(2)O_(3_((s)))+(4)/(3)Cr_((s)),DeltaG^(@)-287KJ` .

10.	The reaction, `Cr_(2)O_(3)+2AlrarrAl_(2)O_(3)+2Cr(DeltaG^(Theta)=-421KJ)` is the thermodynamically feasible as is apparent from the Gibbs energy value . Why does it not take place at rom temperture?
Answer» Certain amount of activation energy is essential even for such reations which are thermodyamically feasible, therefore heating is required .

11.	Explain "Poling".
Answer» when the metals are having the metal oxides as impurities this method is employed. The impure metal is melted and is then covered by carbon powder.Then it is stirred with green wood poles. The reducing gases formed from the green wood the carbon, reduca the oxides to the metal. Eg : Cu & Sn metals are refined by this method.

12.	What is an ore?
Answer» An ore is a mineral from which the metal can be extracted easily and economically. Bauxite is the ore of aluminium.

13.	What is a minneral ?
Answer» The chemical compound from which a metal can be extracted is called a mineral. Bauxite, crayolite are the minerals of aluminium.

14.	What is flux ? Give an example.
Answer» Flux : An outside substance added to ore to lower its melting point is known as flux. `rarr` Flux combines with gangue and forms easily fusible slag. `"gangue "+"Flux "rarr "slag"` Eg : `underset("gangue")(FeO)+underset("Flux")(SiO_(2))rarrunderset("slag")(FeSiO_(3))`

15.	Explain magnetic separation of impurities from an ore.
Answer» Electro-magnetic method : The method is used if the gangue or the ore particles are magnetic in nature. The Finely prwdered ore is dropped on a belt moving on two strong electromagnetic rollers. The magnetic and the non-magnetic substances form two separate heaps. for example ,let the ore particles be magnetic and then the non-magnetic roller. Eg : Haematite and magnetic hae magnetic ore particles. cassiterite or Tin stone has wolframite as magnetic impurity.

16.	What is a ore . Give the of Al,Zn, Zn, Fe, Cu.
Answer» The mineral from which metal can be extracted economically is called ore. `{:("Aluminium ores ",:,"Bauxite"=Al_(2)O_(3).2H_(2)O,,"Cryolite"=Na_(3)AlF_(6)),("Zinc ores",: ,"Zinc blende" =Zns,,"Calamine"=ZnCO_(3)),("Copper ores" ,:, "Cuprite":CuO,,"Copper pyrites"=Cu_(2)S),("Iron ores" ,:,"Haematite"=Fe_(2)O_(3),,"Magnetite"=Fe_(3)O_(4)):}`

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