JEE Main Previous Year Questions (2016- 2024): General Principles & Processes of Isolation Elements | 35 Years Chapter wise Previous Year Solved Papers for JEE PDF Download

Q.1. The purest form of commercial iron is    (2020)
(a) Pig iron
(b) Wrought iron
(c) Cast iron
(d) Scrap iron and pig iron

Ans. b

The purest form of the commercial iron is wrought iron.

Q.2. The refining method used when the metal and the impurities have low and high melting temperatures, respectively, is    (2020)
(a) Liquation
(b) Vapor phase refining
(c) Zone refining
(d) Distillation

Ans. a

Liquation refining is used to separate a low melting metal like, tin from the high melting impurities.

Q.3. Among the reactions (I) – (IV), the reaction(s) that does/do not occur in the blast furnace during the extraction of iron is/are    (2020)
(I) CaO + SiO₂ → CaSiO₃
(II) 3Fe₂O₃ + CO → 2Fe₃O₄ + CO₂
(III) FeO + SiO₂ → FeSiO₃
(IV)
(a) (I)
(b) (I) and (IV)
(c) (III) and (IV)
(d) (IV)

Ans. c

The feasible reactions occur in blast furnace is:

Q.4. According to the following diagram, A reduces BO₂ when the temperature is
    (2020)
(a) < 1400°C
(b) > 1400°C
(c) > 1200°C but < 1400°C
(d) < 1200°C

Ans. b

From the given graph, the line of A intersects B at temperature greater than 1400°C, thus, A can reduce BO₂ at temperature greater than 1400°C.

Q.5. The ore that contains both iron and copper is:    (2019)
(a) copper pyrites
(b) malachite
(c) dolomite
(d) azurite

Ans. a
Amongst the given ores, copper pyrite (CuFeS₂), dolomite (MgCO₃.CaCO₃), malachite [CuCO₃.Cu(OH)₂], azurite [2CuCO₃.Cu (OH)₂], copper pyrite contains both copper and iron.

Q.6. The correct statement regarding the given Ellingham diagram is:    (2019)

(a) At 1400°C, Al can be used for the extraction of Zn from ZnO
(b) At 500°C, coke can be used for the extraction of Zn from ZnO
(c) Coke cannot be used for the extraction of Cu from Cu₂O.
(d) At 800°C, Cu can be used for the extraction of Zn from ZnO

Ans. a
In the given Ellingham diagram, the metal which has a lower value of ΔG° (more negative) can reduce a metal oxide whose curve lies above it. So, Al can reduce ZnO at 1400 °C.

Q.7. Hall-Heroult’s process is given by:    (2019)
(a) Cu²⁺ (aq) + H₂(g) → Cu(s) + 2H⁺ (aq)
(b) Cr₂O₃ + 2AI → Al₂O₃ + 2Cr
(c) 2Al₂O₃ + 3C → 4Al + 3CO₂
(d) ZnO + C  Zn + CO

Ans. c
Hall Heroult’s process is an electrochemical process used in extraction of Al from alumina.

Q.8. Match the ores (column A) with the metals (column B):    (2019)

(a) (I) - (a); (II) - (b); (III) - (c); (IV) - (d)
(b) (I) - (c); (II) - (d); (III) - (b); (IV) - (a)
(c) (I)-(c); (II)-(d); (III)-(a); (IV)-(b)
(d) (I)-(b); (II)-(c); (III)-(d); (IV)-(a)

Ans. b
Siderite = FeCO₃ 
Calamine = ZnCO₃ 
Malachite = CuCO₃.Cu(OH)₂ 
Kaolinite = Al₂Si₂O₅(OH)₄

Q.9. The reaction that does NOT define calcination is:    (2019)
(a)
(b)
(c)
(d)

Ans. b
Calcination involves heating of carbonates or hydrated oxides in absence of air.
 is roasting (heating in a regular supply of air).

Q.10. Match the following items in column I with the corresponding items in column II.    (2019)

(a) (i) → (B); (ii) → (C); (iii) → (A); (iv) → (D)
(b) (i) → (C); (ii) → (B); (iii) → (D); (iv) → (A)
(c) (i) → (D); (ii) → (A); (iii) → (B); (iv) → (C)
(d) (i) → (C); (ii) → (D); (iii) → (B); (iv) → (A)

Ans. d
(i) Na₂CO₃.10H₂O → Solvay process
(ii) Mg(HCO₃)₂ → Temporary hardness
(iii) NaOH → Castner-Kellner process
(iv) Ca₃Al₉O₆ → Portland cement

Q.11. In the Hall-Heroult process, aluminium is formed at the cathode. The cathode is made out of:    (2019)
(a) Pure aluminium
(b) Carbon
(c) Copper
(d) Platinum

Ans. b
In Hall-Heroult process, steel vessel with lining of carbon acts as cathode and graphite is used as anode.

Q.12. The pair that does NOT require calcination is:    (2019)
(a) ZnO and MgO
(b) ZnO and Fe₂O₃.xH₂O
(c) ZnCO₃ and CaO
(d) Fe₂O₃ and CaCO₃.MgCO₃

Ans. a
Calcination involves the conversion of metal carbonates or hydrated oxides into metal oxides. ZnO and MgO are oxides, therefore, does not require calcination.

Q.13. With respect to an ore, Ellingham diagram helps to predict the feasibility of its    (2019)
(a) Electrolysis 
(b) Zone refining
(c) Vapour phase refining
(d) Thermal reduction

Ans. d
Ellingham diagram is a graph showing the temperature dependence of the stability for compounds. It is used to select reducing agent so it helps to predict feasibility of its thermal reduction.

Q.14. The Mond process is used for the:    (2019)
(a) purification of Ni
(b) extraction of Mo
(c) purification of Zr and Ti
(d) extraction of Zn

Ans. a
Mond’s process is used for purification of Ni

Q.15. The ore that contains the metal in the form of fluoride is:    (2019)
(a) cryolite
(b) malachite
(c) magnetite
(d) sphalerite

Ans. a

Q.16. Assertion: For the extraction of iron, haematite ore is used.
Reason: Haematite is a carbonate ore of iron.    (2019)
(a) Only the reason is correct
(b) Both the assertion and reason are correct, but the reason is not the correct explanation for the assertion.
(c) Both the assertion and reason are correct and the reason is the correct explanation for the assertion.
(d) Only the assertion is correct.

Ans. d
For the extraction of iron, haematite ore (Fe₂O₃) is used

Q.17. The one that is not a carbonate ore is:    (2019)
(a) malachite
(b) calamine
(c) siderite
(d) bauxite

Ans. d

Q.18. Match the refining methods (Column I) with metals (Column II).    (2019)

(a) (I) - (c); (II) - (a); (III) - (b); (IV) - (d)
(b) (I) - (b); (II) - (c); (III) - (d); (IV) - (a)
(c) (I)-(c); (II)-(d); (III)-(b); (IV)-(a)
(d) (I)-(b); (II)-(d); (III)-(a); (IV)-(c)

Ans. c
Liquation is used for Sn, zone refining is used for Ga, Mond's process is used for refining of Ni and van Arkel method is used for Zr,
So, correct match is
(I)-(c); (II)-(d); (III)-(b); (IV)-(a)

Q.19. The alloy used in the construction of air crafts is:    (2019)
(a) Mg - Al
(b) Mg - Zn
(c) Mg - Sn
(d) Mg - Mn

Ans. a
In manufacturing of aircraft an alloy of Mg and Al called magnalium is used due to its light weight and high strength.

Q.20. The correct statement is:    (2019)
(a) aniline is a froth stabilizer.
(b) zincite is a carbonate ore.
(c) sodium cyanide cannot be used in the metallurgy of silver.
(d) zone refining process is used for the refining of titanium.

Ans. a
Ti is refined by van Arkel method. Silver is leached by dilute solution of NaCN. Zincite is oxide ore of zinc i.e. ZnO. Aniline is a froth stabilizer.

Q.21. The idea of froth floatation method came from a person X and this method is related to the process Y of ores, X and Y, respectively, are:    (2019)
(a) fisher woman and concentration
(b) washer woman and concentration
(c) fisher man and reduction
(d) washer man and reduction

Ans. b
Froth floatation was discovered by washer woman. It is a method of concentration of ores.

Q.22. The correct statement is:    (2019)
(a) leaching of bauxite using concentrated NaOH solution gives sodium aluminate and sodium silicate.
(b) the Hall-Heroult process is used for the production of aluminium and iron.
(c) pig iron is obtained from cast iron.
(d) the blistered appearance of copper during the metallurgical process is due to the evolution of CO₂.

Ans. a
During metallurgy of aluminium, when bauxite (powdered ore) is treated with NaOH (cone), sodium aluminate (Na[Al(OH)₄]) is formed and impurity (SiO₂) present in bauxite dissolves by forming sodium silicate (Na₂SiO₃)
Al₂O₃(s) + 2NaOH(aq) + 3H₃O(l) → 2Na [Al (OH)₄] (aq)
Cast iron is obtained from pig iron.
Blister of copper is due to evolution of SO₂.
Hall Heroult process is used for the production of aluminium.

Q.23. In the extraction of copper from its sulphide ore, metal is finally obtained by the oxidation of cuprous sulphide with:    (2018)
(a) SO₂
(b) Fe₂O₃
(c) Cu₂O
(d) CO

Ans. c
Cu₂S + 2Cu₂O → 6Cu + SO₂
It is an example of auto-reduction, CuO₂ is reduced to copper metal.

Q.24. Which one of the following ores is best concentrated by froth floatation method?    (2016)
(a) Magnetite
(b) Siderite
(c) Galena
(d) Malachite

Ans. c
PbS, i.e. Galena is best concentrated by froth floatation method.

Q.25. The plot shows the variation of ln Kp versus temperature for the two reactions.


Identify the correct statement:    (2016)
(a) At T > 1200 K, carbon will reduce MO(s) to M(s).
(b) At T < 1200 K, oxidation of carbon is unfavourable.
(c) Oxidation of carbon is favourable at all temperatures.
(d) At T < 1200 K, the reaction MO(s) + C(s) → M(s) + CO(g) is spontaneous.

Ans. d
According to Ellingham diagram, as given

At T < 1200, carbon will reduce MO_(s) to M_(s).
Hence, chemical reaction C_(s) + MO_(s) → M_(s) + CO_(g) is spontaneous.

Q.26. Extraction of copper by smelting uses silica as an additive to remove:    (2016)
(a) FeS
(b) FeO
(c) Cu₂S
(d) Cu₂O

Ans. b