Question 1

In the sequence used during extraction and purification of a metal, a metal sulphide is first converted to a metal oxide, then to an impure metal, and finally to a pure metal: Metal sulphide —x→ Metal oxide —y→ Impure metal —z→ Pure metal. What are x, y and z respectively?

Accepted Answer

roasting, smelting, electrolysis. Metal sulphide is converted to oxide by roasting, the oxide is reduced to impure metal by smelting, and the impure metal is purified to pure metal by electrolysis (electrorefining). So x,y,z = roasting, smelting, electrolysis.

Question 2

In Bayer’s process, which substance is employed as the reagent?

Accepted Answer

Sodium hydroxide. In Bayer's process, powdered bauxite is leached with concentrated sodium hydroxide (NaOH), dissolving Al2O3 as sodium aluminate while impurities like Fe2O3 remain insoluble. So the reagent is sodium hydroxide.

Question 3

Thomas slag refers to which of the following substances?

Accepted Answer

Calcium phosphate, Ca3(PO4)2. Thomas slag, formed in the basic Bessemer process, is mainly calcium phosphate Ca3(PO4)2 and is used as a phosphatic fertilizer.

Question 4

Which of the following fluxes is employed to eliminate acidic impurities during a metallurgical operation?

Accepted Answer

Limestone. To remove acidic impurities a basic flux is used. Limestone (CaCO3, giving basic CaO) combines with acidic impurities to form slag. Silica is an acidic flux used to remove basic impurities.

Question 5

Which material is used to provide a basic lining to a furnace?

Accepted Answer

Calcined dolomite. A basic lining for a furnace is provided by calcined dolomite (CaO.MgO), which is basic and resists basic slag. Silica is an acidic lining; haematite is an iron ore, not a lining material.

Question 6

Electromagnetic separation is employed in the beneficiation of which ore?

Accepted Answer

Cassiterite. Cassiterite (tin stone, SnO2) is non-magnetic but is associated with magnetic wolframite (FeWO4) impurities, so the two are separated by electromagnetic (magnetic) separation. Copper pyrites is concentrated by froth flotation, not magnetic separation.

Question 7

In the cyanide leaching process used for obtaining gold and silver, the metal is subsequently recovered by which method?

Accepted Answer

displacement using zinc. In the Mac-Arthur Forrest cyanide process the metal-cyanide complex is reduced by adding zinc, which displaces gold/silver as the more reactive metal.

Question 8

Which of the following chemical changes best represents calcination?

Accepted Answer

MgCO3 → MgO + CO2. Calcination is heating an ore (usually a carbonate or hydroxide) in limited air to expel volatile matter, e.g. MgCO3 -> MgO + CO2. (2ZnS + 3O2 -> 2ZnO + 2SO2 is roasting; the silver reaction is not calcination.)

Question 9

In pig iron, which impurity is present in the greatest amount?

Accepted Answer

Carbon. Carbon is the primary impurity in pig iron, typically comprising 2-4% of its composition, which significantly influences its properties and is essential for the production of steel.

Question 10

Identify the statement that is not correct among the following:

Accepted Answer

Argentite and cuprite are classified as oxides.. The statement is incorrect because argentite is actually a silver sulfide (Ag2S), while cuprite is a copper oxide (Cu2O). Therefore, classifying both as oxides is inaccurate.

Question 11

Match the items in Column I with those in Column II and choose the correct code from the options given:

Column I
I. Cyanide method
II. Froth flotation
III. Electrolytic extraction
IV. Zone purification

Column II
A. Ultra-pure Ge
B. Pine oil
C. Obtaining Al
D. Obtaining Au

Accepted Answer

I-D, II-B, III-C, IV-A. The cyanide method is specifically used for extracting gold (Au), froth flotation utilizes pine oil as a collector for separating minerals, electrolytic extraction is a common method for obtaining aluminum (Al), and zone purification is a technique used to achieve ultra-pure germanium (Ge).

Question 12

Which of the following statements regarding why sulphide ores are roasted before reduction is incorrect?

Accepted Answer

Carbon and hydrogen are appropriate reducing agents for the reduction of metal sulphides.. Option D is correct because carbon and hydrogen can effectively reduce metal sulphides to their respective metals, making them suitable reducing agents in the process.

Question 13

During the extraction of copper from its sulphide ore, the final step involves reducing cuprous oxide using which substance?

Accepted Answer

Copper(I) sulphide (Cu2S). The final (bessemerisation) step is self-reduction: 2Cu2O + Cu2S -> 6Cu + SO2. Here cuprous oxide is reduced by cuprous sulphide (Cu2S) itself, so the reducing substance is Cu2S.

Question 14

Zone refining of metals works on the principle that

Accepted Answer

impurities dissolve more readily in the melt than in the solid phase. Zone refining relies on the fact that impurities are more soluble in the molten metal than in the solidifying solid. As the molten zone is swept along, impurities concentrate in the melt and are carried to one end, leaving pure metal behind.

Question 15

During the cyanide leaching of silver from argentite, which substances act as the oxidizing agent and the reducing agent, respectively?

Accepted Answer

O2 and Zn dust respectively. In the cyanide leaching process, oxygen (O2) acts as the oxidizing agent by facilitating the oxidation of silver ions, while zinc dust (Zn) serves as the reducing agent, helping to reduce silver ions back to metallic silver.

Question 16

Which of the following metal oxides cannot be converted into the metal by reduction with carbon?

Accepted Answer

Al2O3. Aluminium is more reactive than carbon, so Al2O3 cannot be reduced by C; it is extracted by electrolysis (Hall-Heroult). Fe2O3, PbO and ZnO are all reduced by carbon.

Question 17

During the extraction of copper in a blast furnace, which of the following reactions occurs?

Accepted Answer

All of the above. In the smelting/bessemerization of copper all three reactions take place: roasting 2Cu2S+3O2->2Cu2O+2SO2, oxidation of the iron sulphide impurity 2FeS+3O2->2FeO+2SO2, and the self-reduction 2Cu2O+Cu2S->6Cu+SO2. Hence the correct choice is 'All of the above'.

Question 18

Which purification method is illustrated by the sequence Ti + 2I2 → TiI4 → Ti + 2I2?

Accepted Answer

Van Arkel process. Forming a volatile metal iodide (Ti + 2I2 -> TiI4) and then decomposing it on a hot filament back to pure metal (TiI4 -> Ti + 2I2) is the Van Arkel process, used to obtain ultra-pure Ti and Zr.

Question 19

Which of the following sets consists of oxides that are not reducible by carbon to the corresponding metals?

Accepted Answer

CaO, K2O. Carbon cannot reduce oxides of very electropositive metals like CaO and K2O because these metals have a far greater affinity for oxygen than carbon does (their oxides lie below the carbon line in the Ellingham diagram). Oxides such as Cu2O, SnO2, Fe2O3, ZnO, PbO and Fe3O4 are all reducible by carbon.

Question 20

Which of the following pairs of metals are refined by the van Arkel process?

Accepted Answer

Zr and Ti. The van Arkel (iodide) process purifies Zr and Ti by forming volatile ZrI4/TiI4 which decompose on a hot filament to deposit pure metal. Ni is refined by the Mond process and Fe by other routes.

Question 21

In a blast furnace, which of the following reactions take place in the temperature interval 500–800 K?
(i) Fe2O3 + CO → 2FeO + CO2
(ii) Fe3O4 + 4CO → 3Fe + 4CO2
(iii) FeO + CO → Fe + CO2
(iv) C + CO2 → 2CO

Accepted Answer

(i), (ii) and (iii). In the lower-temperature (500-800 K) upper zone, CO reduces the iron oxides: Fe2O3 -> FeO, Fe3O4 -> Fe and FeO -> Fe, i.e. reactions (i), (ii) and (iii). Reaction (iv) C + CO2 -> 2CO (coke gasification) occurs only at higher temperature (900-1500 K).

Question 22

Which one of the following mineral–formula pairs is mismatched?

Accepted Answer

Zincite – ZnS. Zincite is zinc oxide (ZnO); ZnS is zinc blende/sphalerite. Magnetite Fe3O4, copper glance Cu2S, and calamine ZnCO3 are all correctly matched, so the Zincite-ZnS pair is the mismatched one.

Question 23

Before charging FeO into a blast furnace, it is first roasted to Fe2O3 because

Accepted Answer

it will not be eliminated along with silica as slag. FeO is basic/easily fusible and combines with the silica gangue to form a low-melting slag (FeSiO3), so the iron would be lost in the slag. Roasting it to Fe2O3 first prevents this, so the correct reason is that it will not be eliminated along with silica as slag.

Question 24

Which of the following statements is correct?

Accepted Answer

Fluxes are carefully chosen to combine with the gangue present in the ore to form an easily fusible slag that removes the impurities.. A flux is chosen to combine with the gangue (unwanted earthy impurity) in the ore to form an easily fusible slag, which is then removed. Hence the correct statement is that fluxes combine with the gangue to give slag.

Question 25

When a mixture of cuprous oxide (Cu2O) and cuprous sulfide (Cu2S) is heated, what products are formed?

Accepted Answer

Cu and SO2. On heating, cuprous sulfide and cuprous oxide undergo self-reduction: 2Cu2O + Cu2S -> 6Cu + SO2. The products are copper metal and sulfur dioxide.

Question 26

Parke’s process is employed for

Accepted Answer

separating silver from argentiferous lead. Parke's process separates silver from argentiferous (silver-bearing) lead. Molten zinc is added; silver preferentially dissolves in the zinc layer, which is then skimmed off and distilled, recovering the silver.

Question 27

When sodium formate is heated, what products are formed?

Accepted Answer

Sodium oxalate and hydrogen gas. When sodium formate is heated, it undergoes a decomposition reaction that produces sodium oxalate and hydrogen gas as the primary products.

Question 28

Which of the following ore is concentrated using group 1 cyanide salt?

Accepted Answer

Sphalerite. Sphalerite, which is primarily composed of zinc sulfide, is effectively concentrated using cyanide salts due to the ability of cyanide to selectively bind with zinc ions, facilitating their extraction during the processing of the ore.

Question 29

In the Hall–Héroult process, aluminium is obtained by electrolysing which material?

Accepted Answer

alumina dissolved in molten cryolite. The Hall–Héroult process specifically involves the electrolysis of alumina that is dissolved in molten cryolite, as this mixture lowers the melting point and improves the efficiency of the electrolysis process.

Question 30

Which metal is obtained by leaching with a cyanide solution?

Accepted Answer

Ag. Silver is commonly extracted from its ores through a process called cyanidation, where a cyanide solution selectively dissolves silver, allowing for its recovery.

Question 31

Which of the following ores is most suitably concentrated by the froth-flotation process?

Accepted Answer

Galena. Froth flotation is used for sulphide ores. Galena (PbS) is a sulphide and is concentrated by froth flotation; magnetite, cassiterite and malachite are oxide/carbonate ores.

Question 32

Which of the following considerations is not relevant to the practice of first roasting sulphide ores to their oxides instead of reducing the sulphides directly with carbon?

Accepted Answer

Metal sulphides are less stable than the corresponding oxides. This option is correct because the stability of metal sulphides compared to their oxides is not a relevant consideration for the roasting process; instead, the focus is on the thermodynamic favorability of the roasting reaction itself.

Question 33

The reactions below illustrate which purification technique?

Ti(s) + 2I2(g) 523 Kb7b7b7b7b7b7 TiI4(g)
TiI4(g) b1700 Kb7b7b7b7b7b7 Ti(s) + 2I2(g)

Accepted Answer

van Arkel method. The van Arkel method is a purification technique that involves the formation and subsequent decomposition of a volatile compound, in this case, titanium iodide (TiI4), allowing for the separation of pure titanium from impurities.

Question 34

Which of the following ores is most suitably concentrated by the froth flotation process?

Accepted Answer

Galena. Galena, which is primarily composed of lead sulfide, is effectively concentrated using the froth flotation process due to its hydrophobic properties, allowing it to separate from other minerals in an aqueous solution.

Question 35

Which ore contains both iron and copper?

Accepted Answer

Copper pyrites. Copper pyrites, also known as chalcopyrite, is a sulfide mineral that is a primary source of both copper and iron, making it the correct choice among the options provided.

Question 36

Which of the following ores contains the metal in the form of a fluoride compound?

Accepted Answer

Cryolite. Cryolite is a mineral that contains aluminum in the form of a fluoride compound, specifically sodium aluminum fluoride (Na3AlF6), making it the correct choice among the options provided.

Question 37

Heating mixture of Cu2O and Cu2S will give

Accepted Answer

Cu + SO2. When Cu2O (copper(I) oxide) and Cu2S (copper(I) sulfide) are heated together, they undergo a reduction reaction that produces elemental copper (Cu) and sulfur dioxide (SO2) as a result of the oxidation of sulfur from Cu2S.

Question 38

Galvanization is applying a coating of:

Accepted Answer

Zn. Galvanization involves coating iron or steel with zinc to protect it from corrosion, as zinc acts as a sacrificial anode, preventing rusting of the underlying metal.

Question 39

Which one of the following ores is best concentrated by froth floatation method ?

Accepted Answer

Galena. Galena is best concentrated by froth flotation because it is a sulfide mineral that has a high density and hydrophobic properties, allowing it to effectively separate from gangue materials in the flotation process.

Question 40

In the extraction of copper from its sulphide ore, metal is finally obtained by the oxidation of cuprous sulphide with -

Accepted Answer

Cu2O. In the Bessemerisation step copper is obtained by self-reduction: 2Cu2O + Cu2S -> 6Cu + SO2. Here cuprous sulphide is oxidised by cuprous oxide (Cu2O), so the oxidising agent is Cu2O.

Question 41

The ore that contains both iron and copper is -

Accepted Answer

copper pyrites. Copper pyrites, CuFeS2 (chalcopyrite), contains both iron and copper. Dolomite is Ca/Mg, while malachite and azurite are copper-only carbonate ores. So the correct choice is copper pyrites.

Question 42

The Mond process is used for the-

(1) purification of Ni
(2) extraction of Zn
(3) extraction of Mo
(4) purification of Zr and Ti

Accepted Answer

purification of Ni. The Mond process specifically involves the conversion of nickel into a volatile carbonyl compound, which can then be decomposed to yield pure nickel, making it an effective method for purifying nickel.

Question 43

Match the refining methods (Column I) with metals (Column II).
Column I (Refining methods): (I) Liquation, (II) Zone Refining, (III) Mond Process, (IV) Van Arkel Method
Column II (Metals): (a) Zr, (b) Ni, (c) Sn, (d) Ga

Accepted Answer

(I)-(c); (II)-(d); (III)-(b); (IV)-(a). Liquation refines low-melting Sn (c); zone refining purifies Ga/semiconductors (d); the Mond process refines Ni (b); the van Arkel method purifies Zr (a). Thus (I)-c, (II)-d, (III)-b, (IV)-a.

Question 44

The one that is not a carbonate ore is: (1) malachite (2) bauxite (3) calamine (4) siderite

Accepted Answer

bauxite. Bauxite is primarily an aluminum ore and does not contain carbonate minerals, while malachite, calamine, and siderite are all carbonate ores.

Question 45

Match the ores (column A) with the metals (column B):
(Column A) ores
(I) Siderite
(II) Kaolinite
(III) Malachite
(IV) Calamine

(Column B) metals
(a) Zinc
(b) Copper
(c) Iron
(d) Aluminium

Accepted Answer

(I)-(c); (II)-(d); (III)-(b); (IV)-(a). The correct option matches each ore with its corresponding metal: Siderite is an iron ore, Kaolinite is a clay mineral associated with aluminum, Malachite is a copper ore, and Calamine is a zinc ore, accurately reflecting their known associations.

Question 46

Cast iron is used for the manufacture of:

Accepted Answer

wrought iron and steel. Cast iron is remelted/refined to manufacture wrought iron (by removing carbon) and steel (by controlled decarburisation). Pig iron is the raw material made before cast iron, so it is not manufactured from cast iron. Correct: 'wrought iron and steel'.

Question 47

Among statements (a) – (d), the correct ones are- (a) Lime stone is decomposed to CaO during the extraction of iron from its oxides (b) In the extraction of silver, silver is extracted as an anionic complex (c) Nickel is purified by Mond's process (d) Zr and Ti are purified by Van Arkel me

Accepted Answer

(4) (a), (b), (c) and (d). (a) Limestone decomposes to CaO (flux) in the blast furnace - true. (b) Silver is leached as the anionic complex [Ag(CN)2]^- - true. (c) Nickel is purified by Mond's carbonyl process - true. (d) Zr and Ti are purified by the Van Arkel method - true. So all four are correct.

Question 48

An Ellingham diagram provides information about:
(1) the pressure dependence of the standard electrode potentials of reduction reactions involved in the extraction of metals.
(2) the kinetics of the reduction process.
(3) the temperature dependence of the standard Gibbs energies of formati

Accepted Answer

the temperature dependence of the standard Gibbs energies of formation of some metal oxides.. An Ellingham diagram plots the standard Gibbs energy of formation of metal oxides versus temperature, showing its temperature dependence. (The pH/potential stability description is a Pourbaix diagram.)

Question 49

The INCORRECT statement is -

Accepted Answer

Brass is an alloy of copper and nickel. The correct option is wrong because brass is actually an alloy of copper and zinc, not copper and nickel.

Question 50

Among the reactions (a)-(d), the reaction(s) that does/do not occur in the blast furnace during the extraction of iron is/are:
(a) CaO + SiO2 → CaSiO3
(b) 3Fe2O3 + CO → 2Fe3O4 + CO2
(c) FeO + SiO2 → FeSiO3
(d) FeO → Fe + 1/2 O2

Accepted Answer

(c) and (d). Added limestone gives CaO, which combines with SiO2 to form slag (reaction a occurs), so FeO + SiO2 -> FeSiO3 (c) does not take place. Direct decomposition FeO -> Fe + 1/2 O2 (d) also does not occur. Hence (c) and (d) are the reactions that do not occur.

JEE Main Chemistry: General Principles of Isolation of Elements questions with solutions

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