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General Principles of Isolation of Elements · Question 13

NEET 2013 (Karnataka)MCQEasy📈 Topic in 25% papers+4−1
1

The metal oxide which cannot be reduced to metal by carbon is

  1. Al2O3
  2. PbO
  3. ZnO
  4. Fe2O3

Answer

(1) Al2O3

Solution

As per NCERT, aluminium is highly electropositive and its oxide is very stable; in the Ellingham diagram the f G line of Al2O3 lies far below that of CO in the usual temperature range, so carbon cannot reduce Al2O3.

Aluminium is extracted by electrolytic reduction of alumina (Hall-Heroult process), while PbO, ZnO and Fe2O3 are reduced by carbon / CO.

Answer: (1)

Out of syllabusNEET 2013 (Karnataka)

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2

The Gibbs energy for the decomposition of Al2O3 at 500 is as follows 23Al2O3 43Al + O2 rG = +960 kJ mol-1 The potential difference needed for the electrolytic reduction of aluminium oxide (Al2O3) at 500 is at least

  1. 4.5 V
  2. 3.0 V
  3. 2.5 V
  4. 5.0 V
AIPMT 2012 (Mains)
3

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

  1. carbon monoxide
  2. copper (I) sulphide
  3. sulphur dioxide
  4. iron (II) sulphide.
Out of syllabusAIPMT 2012 (Prelims)
4

Aluminium is extracted from alumina (Al2O3) by electrolysis of a molten mixture of

  1. Al2O3 + HF + NaAlF4
  2. Al2O3 + CaF2 + NaAlF4
  3. Al2O3 + Na3AlF6 + CaF2
  4. Al2O3 + KF + Na3AlF6
Out of syllabusAIPMT 2012 (Prelims)
5

Which one of the following is a mineral of iron?

  1. Malachite
  2. Cassiterite
  3. Pyrolusite
  4. Magnetite
Out of syllabusAIPMT 2012 (Prelims)
6

The following reactions take place in the blast furnace in the preparation of impure iron. Identify the reaction pertaining to the formation of the slag.

  1. Fe2O3(s) + 3CO(g) 2Fe(l) + 3CO2(g)
  2. CaCO3(s) CaO(s) + CO2(g)
  3. CaO(s) + SiO2(s) CaSiO3(s)
  4. 2C(s) + O2(g) 2CO(g)
Out of syllabusAIPMT 2011 (Mains)
7

Which of the following elements is present as the impurity to the maximum extent in pig iron?

  1. Manganese
  2. Carbon
  3. Silicon
  4. Phosphorus
Out of syllabusAIPMT 2011 (Prelims)
8

Which of the following pairs of metals is purified by van Arkel method?

  1. Ga and In
  2. Zr and Ti
  3. Ag and Au
  4. Ni and Fe
Out of syllabusAIPMT 2011 (Prelims)
9

Sulphide ores of metals are usually concentrated by froth flotation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

  1. Galena
  2. Copper pyrite
  3. Sphalerite
  4. Argentite
Out of syllabusAIPMT 2007
10

Which of the following statements about the advantage of roasting of sulphide ore before reduction is not true?

  1. The fG of the sulphide is greater than those for CS2 and H2S.
  2. The fG is negative for roasting of sulphide ore to oxide.
  3. Roasting of the sulphide to the oxide is thermodynamically feasible.
  4. Carbon and hydrogen are suitable reducing agents for metal sulphides.
Out of syllabusAIPMT 2007
11

The mass of carbon anode consumed (giving only carbon dioxide) in the production of 270 kg of aluminium metal from bauxite by the Hall process is (Atomic mass : Al = 27)

  1. 270 kg
  2. 540 kg
  3. 90 kg
  4. 180 kg
AIPMT 2005

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