JEE Main 35 Year PYQs- General Principles and Processes of Isolation Elements

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 1

Aluminium is extracted by the electrolysis of [2002]

A.
bauxite
B.
alumina
C.
alumina mixed with molten cryolite
D.
molten cryolite.

Detailed Solution: Question 1

Pure aluminium can be obtained by electrolysis of a mixture containing alumina, crayolite and fluorspar in the ratio 20 : 24 : 20. The fusion temperature of this mixture is 900ºC and it is a good conductor of electricity

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 2

The metal extracted by leaching with a cyanide is [2002]

A.
Mg
B.
Ag
C.
Cu
D.
Na.

Detailed Solution: Question 2

Silver ore forms a soluble complex with NaCN from which silver is precipitated using scrap zinc.

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Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 3

Which one of the following ores is best concentrated byfroth-flotation method ? [2004]

A.
Magnetite
B.
Cassiterite
C.
Galena
D.
Malachite

Detailed Solution: Question 3

Froth flotation method is used for the concentration of sulphide ores. The method is based on the preferential wetting properties with the frothing agent and water. In the given options, Galena (PbS) is the only sulphide ore.

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 4

During the process of electrolytic refining of copper, some metals present as impurity settle as ‘anode mud’. These are [2005]

A.
Fe and Ni
B.
Ag and Au
C.
Pb and Zn
D.
Sn and Ag

Detailed Solution: Question 4

During the process of electrolytic refining Ag and Au are obtained as anode mud.

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 5

Which of the following factors is of no significance forroasting sulphide ores to the oxides and not subjecting thesulphide ores to carbon reduction directly? [2008]

A.
Metal sulphides are thermodynamically more stablethan CS₂
B.
CO₂ is thermodynamically more stable than CS₂
C.
Metal sulphides are less stable than the correspondingoxides
D.
CO₂ is more volatile than CS₂

Detailed Solution: Question 5

NOTE : The reduction of metal sulphides by carbon reduction process is not spontaneous because DG for such a process is positive. The reduction of metal oxide
by carbon reduction process is spontaneous as DG for such a process is negative.
From this we find that on thermodynamic considerations CO₂ is more stable than CS₂ and the metal sulphides are more stable than corresponding oxides.
In view of above the factor listed in choice (c) is incorrect and so is of no significance.
Hence the correct answer is (c)

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 6

29.5 mg of an organic compound containing nitrogen wasdigested according to Kjeldahl’s method and the evolvedammonia was absorbed in 20 mL of 0.1 M HCl solution. Theexcess of the acid required 15 mL of 0.1 M NaOH solutionfor complete neutralization. The percentage of nitrogen inthe compound is [2010]

A.
59.0
B.
47.4
C.
23.7
D.
29.5

Detailed Solution: Question 6

Moles of HCl taken = 20 × 0.1 × 10^–3 = 2 × 10^–3
Moles of HCl neutralised by NaOH solution
= 15 × 0.1 × 10^–3 = 1.5 × 10^–3
Moles of HCl neutralised by ammonia
= 2 × 10^–3 – 1.5 × 10^–3
= 0.5 × 10^–3

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 7

Which method of purification is represented by the following equation ? [2012]

A.
Zone refining
B.
Cupellation
C.
Polling
D.
Van Arkel

Detailed Solution: Question 7

Van Arkel is a method in which heat treatment is used to purify metal in this process metals are converted into other metal compound for loosly coupled like as iodine to make metal iodide which are easily decomposed and give pure metal.
The process is known as Van Arkel method.

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 8

The metal that cannot be obtained by electrolysis of anaqueous solution of its salts is: [JEE M 2014]

A.
Ag
B.
Ca
C.
Cu
D.
Cr

Detailed Solution: Question 8

On electrolysis of aqueous solution of s-block elements H₂ gas discharge at cathode.

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 9

In the context of the Hall - Heroult process for the extraction of Al, which of the following statements is false ?[JEE M 2015]

A.
Al³⁺ is reduced at the cathode to form Al
B.
Na₃AlF₆ serves as the electrolyte
C.
CO and CO₂ are produced in this process
D.
Al₂O₃ is mixed with CaF₂ which lowers the melting pointof the mixture and brings conductivit 112y

Detailed Solution: Question 9

In Hall-Heroult process,
2 Al₂O₃+ 3 C → 4 Al + 3CO₂
Oxygen liberated at anode reacts with carbon anode to give CO and CO₂.

Na₃AlF₆ (cryolite) or CaF₂ is mixed with purified Al₂O₃ to lower the melting point for easier electrolysis.

Test: JEE Main 35 Year PYQs- General Principles & Processes of Isolation of Elements - Question 10

Which one of the following ores is best concentrated byfroth floatation method? [JEE M 2016]

A.
Galena
B.
Malachite
C.
Magnetite
D.
Siderite

Detailed Solution: Question 10

Froth floatation method is mainly applicable for
sulphide ores.
(1) Malachite ore : Cu(OH)₂ . CuCO₃
(2) Magnetite ore : Fe₃O₄
(3) Siderite ore : FeCO₃
(4) Galena ore : PbS (Sulphide Ore)

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JEE Main 35 Year PYQs- General Principles & Processes of Isolation Elements

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