Isolation of Elements Test 2

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Isolation of Elements Test 2

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Question 1
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Only One Option Correct Type
This section contains 10 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONLY ONE is correct
Q.
Which represents the correct abundance order of elements in the earth crust?

A
O > Si > Fe > Al

B
O > Si > AI > Fe

C
O > C > Si > AI

D
AI > Fe > 0 > Si

Solution

The mass-abundance of the nine most abundant elements in the Earth's crust is approximately: oxygen 46%, silicon 28%, aluminum 8.3%, iron 5.6%, calcium 4.2%, sodium 2.5%, magnesium 2.4%, potassium 2.0%, and titanium 0.61%.
Question 2
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Which of the following contains both copper and iron?

A
Cuprite

B
Chalcocite

C
Chalcopyrite

D
Malachite

Solution

Chalcopyrite (CuFeS2) is the ore which contains both copper and iron.
Question 3
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Regarding cryolite incorrect statement is

A
It is an ore of Al

B
The non-metal is fluorine

C
It is used in aluminium extraction from bauxite

D
Its formula is 3NaF. AIF₃

Solution

Cryolite (Na₃AIF₆) is used in the manufacture of aluminium. Electrolysis of (Al₂O₃) dissolved in molten Na₃AIF₆.
Question 4
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In chromite ore, the oxidation number iron and chromium are respectively ______.

A
+3, + 6

B
+3, + 2

C
+2, + 3

D
+2, + 6

Solution

In chromite ore is (FeO . Cr₂O₃)
Let the oxidation state of Fe be x.
∴ x - 2 + 2 x 3 + 3 x (-2) = 0
x - 2 + 6 - 6 = 0 ⇒ x = + 2
Let the oxidation state of Cr be y
∴ 2 y + 2 - 2 + 3 x (-2 ) = 0
2 y - 6 = 0
y = 3
Hence, oxidation state of Fe and Cr are +2 and +3 respectively.
Question 5
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Sulphide ores are common for metals

A
Ag, Cu and Pb

B
Ag, Cu and Sn

C
Ag, Mg and Pb

D
Al, Cu and Pb

Solution

Metals having high polarising power (Z_eff) exist in ore with anions having high polarisibility
Ag, Cu, Pb →Sulphide ores (Ag₂S, CuFeS₂, Pbs)
Sn → Oxide ore (SnO₂)
Mg→Sea water and dolomite (CaCO₃, MgCO₃)
Al →Oxide ore (Al₂O₃.2H₂O)
Question 6
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Oxidation states of the metal in the minerals haematite and magnetite respectively are

A
II, III in haematite and III in magnetite

B
II, III in haematite and II in magnetite

C
II in haematite and II, III in magnetite

D
Ill in haematite and II, III in magnetite

Solution

Haematite is Fe₂O₃, in which oxidation number of iron is III. Magnetite is Fe₃O₄ which is infact a mixed oxide (FeO.Fe₂O₃), hence iron is present in both II and III oxidation state.
Question 7
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Among the following statements the incorrect one is

A
Calamine and siderite are carbonate ores

B
Argentite and cuprite are oxides

C
Zinc blende and pyrites are sulphide ores

D
Malachite and azurite are ores of copper

Solution

Statement: Zinc blende and iron pyrites are sulphides. This statement is correct because zinc blende is ZnS and iron pyrites is FeS₂.
Statement:Calamine and siderite are carbonates. This statement is correct because calamine is ZnCO₃ and siderite is FeCO₃.
Statement: Malachite and azurite are ores of copper. This statement is also correct because malachite is Cu(OH)₂.CuCO₃ and azurite isCu(OH)₂.2CuCO₃.
Statement: Argentite and cuprite are oxides. This statement is incorrect because argentite is Ag₂S and cuprite is Cu₂O.
Question 8
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A mineral is called an ore if

A
the percentage of metal content is more than 50 %

B
it is possible to isolate metal from it

C
a metal can be profitably extracted from it

D
if it is free from any earthly impurities

Solution

A mineral is called an ore if a metal can be profiteably extracted from it. e.g. Aluminium occur in earth's crust in the form of two minerals i.e. bauxite (Al₂O₃ . 2H₂O) and clay (Al₂O₃ . 2SiO₂ . 2H₂O). Out of these two minerals aluminium can be conveniently and economically extracted from bauxite while no easy and cheap method is so far available for the extraction of aluminium from clay. Therefore, the ore of aluminium is bauxite.
Question 9
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Which is incorrect match?

A
Calamine = ZnCO₃

B
Siderite = Fe3O₄

C
Sphalerite = ZnS

D
Malachite = CuCO₃ . Cu(OH)₂

Solution

Siderite is a mineral composed of iron(II) carbonate (FeCO₃)
Question 10
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The molecular formula of Glauber's salt is:

A
MgSO₄ . 7H₂O

B
FeSO₄ . 7H₂O

C
CuSO₄ . 5H₂O

D
Na₂SO₄ . 10H₂O

Solution

Glauber's salt, common name for sodium sulfate decahydrate, Na₂SO₄.10H₂O. It occurs as white or colorless monoclinic crystals. Upon exposure to fairly dry air, it effloresces, forming powdery anhydrous sodium sulfate.
Question 11
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Comprehension Type
This section contains a passage describing theory, experiments, data, etc. Two questions related to the paragraph have been given. Each question has only one correct answer out of the given 4 options (a), (b), (c) and (d)
Passage
The natural substances in which metals occur in the earth are called minerals. A mineral has a definite composition. It may be a single compound or a complex mixture . It is usually associated with number of impurities. The minerals from which the metals can be conveniently extracted are called ores .Thus, all ores are minerals but all minerals are not ores. Depending on the composition ores are classified into different types such as oxides, sulphides, carbonates, halides, silicates etc.
Q. The impurities associated with minerals are called.

A
Gangue

B
Flux

C
Slag

D
Depressant

Solution

The correct answer is option A
The impurities associated with minerals used in metallurgy are collectively called Gangue.
Question 12
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The natural substances in which metals occur in the earth are called minerals. A mineral has a definite composition. It may be a single compound or a complex mixture . It is usually associated with number of impurities. The minerals from which the metals can be conveniently extracted are called ores .Thus, all ores are minerals but all minerals are not ores. Depending on the composition ores are classified into different types such as oxides, sulphides, carbonates, halides, silicates etc.
Q.
Metals that exist in their native state are

A
Cu and Fe

B
Al and Cu

C
Au and Pt

D
Pd and Pt

Solution

Elements which are not attached by moisture, oxygen and carbon dioxide of the air occur in the native state, e.g. Au, Pt, and noble gases.
Question 13
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Matching List Type
Choices for the correct combination of elements from Column I and Column II are given as options (a), (b), (c) and (d), out of which one is correct.
Q.
Match the Column I with Column II and mark the correct options from the codes given below

A

B

C

D

Solution

(i) → (t), (ii) → (s), (iii) → (q), (iv) → (p)
Question 14
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Match the Column I with Column II and mark the correct option from the codes given below.

A

B

C

D

Solution

(i) → (r), (ii) → (s), (iii) → (p), (iv) → (q,t)