Principles & Isolation of Elements Test

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Principles & Isolation of Elements Test - 2

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Question 1
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Only One Option Correct Type
Direction : This section contains 9 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONLY ONE is correct.
Q.
Ellingham diagram represents a graph of

A
ΔG vsT

B
ΔG °vs T

C
ΔS °vs T

D
ΔG vs P

Solution

Eilingham diagram represents a graph of ΔG °vs T.
Question 2
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ΔG °vsT plot in the Ellingham diagram slopes down for the reaction.

A

B

C

D

Solution

In the case of carbon reacting with dioxygen.

two volumes of CO for every one volume of dioxygen used. Thus, ΔS is positive and hence ΔG becomes increasilngly negative as temperature increases. Consequently the line on Eilingham diagram slope downwards.
Question 3
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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.

A
Fe₂ O₃ (s) + 3CO (g) →2 Fe (l) +3CO₂ (g)

B
CaCO₃ (s) →CaO (s) + CO₂ (g)

C
CaO (s) +SiO₂ →CaSiO₃ (s)

D
2C (s) + O₂ (g) →2 CO(g)

Solution

A slag is an easily fusible material which is formed when gangue still present in the roasted or the calcined ore combines with the flux. For example, in the metallurgy of iron, CaO (flux) combines with silica gangue to form easily fusible calcium silicate (CaSiO₃ ) slag.
CaO + SiO₂ →CaSiO₃ (slag)
Question 4
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Which metal has a greater tendency to form metal oxide?

A
Cr

B
Fe

C
Al

D
Ca

Solution

Because the change in free energy i.e. ΔG is highly negative for this reaction,
Question 5
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The main reaction occurring in blast furnace during the extraction of iron from haematite is

A
Fe₂ O₃ + 3CO →2Fe + 3CO₂

B
FeO + SiO₂ →FeSiO₃

C
Fe₂ O₃ + 3C →2Fe + 3CO

D
CaO + SiO₂ →CaSiO₃

Solution

3Fe₂ O₃ + CO →2Fe₃ O₄ + CO₂
Fe₃ O₄ + CO →3FeO + CO₂
FeO + CO →Fe + CO₂
Question 6
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Consider the following reactions at 10000 °C,
Then choose the correct statement from the following.

A
Zinc can be oxidised by CO

B
ZnO can be reduced by CO

C
ZnO can be reduced by C

D
None of the above

Solution

Because the ΔG °of the formation of CO is more negative than that of ZnO at 10000 °C.
Question 7
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According to Ellingham diagrams the oxidation reaction of carbon and carbon monoxide may be used to reduce which one of the following oxides at the lowest temperature?

A
Al₂ O₃

B
ZnO

C
MgO

D
Cu₂ O

Solution

Because ΔG °for reductions of rest three oxides [Al₂ O₃ , ZnO and MgO] are less negative than that of Cu₂ O at lower temperature.
Question 8
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The minimum voltage required to electrolyse alumina in the Hall-Heroult process is [Given, (Al₂ O₃ ) = - 1520 kJ/mol and (CO₂ ) = 394 k J/mol]

A
1.575

B
1.60 V

C
1.312 V

D
-2.62 V

Solution

In Hall - Heroult process the following reactions occur
Question 9
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Based on the given information (CaO) = - 604.2 kJ/mol and (Al₂ O₃ ) = - 1582 kJ/mol, which of the following is feasible?

A
3CaO + 2AI →AI₂ O₃ + 3C

B
3Ca + AI₂ O₃ →2AI + 3CaO

C
Both (a) and (b)

D
None of the above

Solution

3Ca + Al₂ O₃ →2AI + 3CaO
ΔG °= 3 x (CaO) - (Al₂ O₃ )
= 3 x (-604.2)-(-1582)
= -1812 + 1582 = -230 kJ
ΔG °is negative. Hence, this reaction is feasible.
Question 10
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One or More than One Options Correct Type

Direction : This section contains 5 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.

Q.

For the metallurgical process of which of the calcined ore can be reduced by carbon?

A
Haemat

B
Calamine

C
Iron pyrites

D
Zincite

Solution

Calcined ore of haematite (Fe₂ O₃ ) and zincite (ZnO) can be reduced by carbon.