Principles & Isolation of Elements Test

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Principles & Isolation of Elements Test - 3

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Weekly Quiz Competition

Question 1
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For which oxide formation ΔG °is more negative than Gr₂ O₃ ?

A
FeO

B
ZnO

C
Al₂ O₃

D
MgO

Solution

According to Eilingham diagram, for Al₂ O₃ and MgO is more negative than Cr₂ O₃ .
Question 2
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In the extraction of iron from haematite in blast furnace reducing agent

A
At low temperature CO is effective

B
At high temperature carbon is more effective

C
Both carbon and CO are effective at any temperature

D
Carbon is effective at low temperature and CO at high temperature

Solution

The correct answer is option
Carbon monoxide is the actual reducing agent of haematite in blast furnace.

C + O₂ →CO₂ ↑
CO₂ + C →2CO ↑
Fe₂ O₃ + CO →2FeO + CO₂ ↑
FeO + CO →Fe + CO₂ ↑
Question 3
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Based on the given information, (CaO) = -604.2 kJ/mol and (Al₂ O₃ ) = - 1582 kJ/mol, which o f the following is correct?

A
3CaO + 2AI →Al₂ O₃ + 3Ca, is spontaneous

B
3CaO + 2AI →AI₂ O₃ + 3Ca, is non-spontaneous

C
ΔG °for the reaction 3 CaO + 2Al →Al₂ O₃ + 3Ca, is + 230.6

D
ΔG °for the reaction 3CaO + 2AI →Al₂ O₃ + 3Ca, is - 977.8

Solution

3CaO + 2AI →Al₂ O₃ + 3Ca
ΔG °= (Al₂ O₃ ) - 3 (CaO)
= - 1582 - 3 (-604)
= -1582 + 1812 = +230 kJ
ΔG °is positive. Hence this reaction is not spontaneous.
Question 4
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Consider the Ellingham diagram given below. Which metal(s) in the diagram can be extracted at 1100 K using coke as a reducing agent?

A
Ca, Al

B
Ca, Al, Zn, Fe

C
Zn, Fe

D
Ni

Solution

In the extraction of iron, at low temperature CO is effective and at high temperature carbon is more effective.
Question 5
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Comprehension Type

Direction : This section contains a paragraph, describing theory, experiments, data, etc. Two questions related to the paragraph have been given. Each question has only one correct answer among the four given options (a), (b), (c) and (d).

Passage

Q.

To make the reduction ZnO+ C →Zn + CO spontaneous, temperature should be

A
<1000 °C

B
>1000 °C

C
<500 °C

D
>500 °C but <1000 °C

Solution

The temperature should be above the intersecting temperature.
Question 6
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Passage

Q.

At 1100 °C, which reaction is spontaneous to a maximum extent ?

A
MgO + C →Mg + C

B
ZnO + C →Zn + CO

C
MgO + Zn →Mg + ZnO

D
ZnO + Mg →Zn + Mg

Solution

At 1100 °C the ΔG °for
ZnO + Mg →Zn + MgO, is more negative then other three reactions.
Question 7
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Matching List Type

Direction : 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 option from the codes given below.

A

B

C

D

Solution

(i) →(q), (ii) →(r), (iii) →(s), (iv) →(p)
Question 8
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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,t), (ii) →(p), (iii) →(s), (iv) →(q)
Question 9
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One Integer Value Correct Type

Direction : This section contains 5 questions. When worked out will result in an integer from 0 to 9 (both inclusive).

Q.

In the Gibbs equation at equilibrium the value of ΔG is

A
0

B
340

C
5023

D
1027

Solution

ΔG = ΔH-T &S
At eqbm. (ΔG = 0)
0 = ΔH - 7 ΔS ⇒ΔH = T ΔS
Question 10
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The reaction 3CaO + 2AI →Al₂ O₃ + 3Ca is non-spontaneous. The number of electrons involved are

A
6

B
346

C
5623

D
1627

Solution

3CaO + 2Al Al₂ O₃ + 3Ca
At anode: 2Al(s) 2Al³⁺ + 6e-
At cathode: 3Ca²⁺ + 6e^- 3Ca(s)
Hence, number of e- involved = 6
Question 11
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The given reaction 2AI + Cr₂ O₃ →Al₂ O₃ + 2Cr is spontaneous. The number of electrons involved are

A
6

B
346

C
5623

D
1627

Solution

6 electrons from 2 Al-atoms participate.
Question 12
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Among PbO, ZnO, CaO, Al₂ O₃ , SnO₂ , Cr₂ O₃ , WO₃ , HgO the oxides reduced by carbon are

A
3

B
343

C
5323

D
1327

Solution

PbO, ZnO and SnO₂ are reduced by carbon.
Question 13
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Cu²⁺ + Fe →Cu + Fe²⁺ for this reaction to calculate ΔG °the formula ΔG °= - nFE °is used. Here, value of n is

A
2

B
342

C
5223

D
1227

Solution

ΔG °= -nFE °, n = number of electrons involved
Question 14
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Statement Type

Direction : This section is based on Statement I and Statement II. Select the correct answer from the codes given below.

Q.

Statement I : Carbon is good reducing agent for sulphides.

Statement II : Carbon is poor reducing agent for iron oxide.

A
Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I

B
Both Statement I and Statement II are correct and Statement II is not the correct explanation of Statement I

C
Statement I is correct but Statement II is incorrect

D
Statement II is correct but Statement I is incorrect

Solution

Carbon is a good reducing agent for oxides, it is a poor reducing agent for sulphides. The reason why carbon reduces so many oxides at elevated temperature is that the ΔG °/T line for CO has a negative slope. There is no compound as analogous to CO with a steep negative ΔG °/T line. Thus sulphides are normally roasted in air to form oxides before reducing with carbon
2 MS + 3O₂ →2MO + 2SO₂
Question 15
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Statement I : Carbon can reduce Fe₂ O₃ to Fe at a temperature below 983 K.

Statement II : Iron has higher affinity toward oxygen than carbon.

A
Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I

B
Both Statement I and Statement II are correct and Statement II is not the correct explanation of Statement I

C
Statement I is correct but Statement II is incorrect

D
Statement II is correct but Statement I is incorrect

Solution

Below 983 K iron having higher affinity towards oxygen than carbon, carbon cannot reduce Fe₂ O₃ to Fe.