General Principles and Processes of Isolation of Elements Test

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General Principles and Processes of Isolation of Elements Test - 57

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Question 1
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All minerals are not the ore but all ores are minerals. The extraction of a particular metal depends upon several factors and overall it has to be convenient and economical.

Which of the following statement is true?

A
Na-ethyl xanthate is used as frother exclusively.

B
Levigation cannot be applied for sulphide in any condition.

C
Froth floatation can be applied for non-sulphide ore also using suitable activator.

D
Impurities like S and As are removed as elemental vapor in roasting.

Solution

(A) Sodium ethylxanthate acts as collector and not frother.

(b) Levigation can be used for sulphide ore to remove majority of gangue when density difference is high.

(C) Froth floatation can be used for non-sulphide ores having sulphide impurities, and the ore is recovered by using suitable activator.

(D) During roasting, impurities such as S and As are removed as their volatile oxides $$SO_2$$ and $$As_2O_3$$, respectively.

Hence, only option C is true.
Question 2
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Find out C in the given flowchart:

A
$$CO_2$$

B
$$SO_2$$

C
$$SO$$

D
$$NO_2$$

Solution

By this process, Aluminium is extracted from alumina.

Reaction:
$$Al_2O_3.2H_2O \xrightarrow {conc. Na_2CO_3} Na[Al(OH)_4] \xrightarrow {CO_2} Al_2O_3 \xrightarrow {Mix with Na_3AlF_6} Al$$
A B C D E F

Therefore, C is $$CO_2$$
Question 3
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Which one of the following oxides is reduced by water gas to obtain the metal during its extraction?

A
$$NiO$$

B
$$ZnO$$

C
$$WO_{3}$$

D
$$Fe_{2}O_{3}$$

Solution

$$2NiO+CO+H_2 \rightarrow 2Ni+CO_2+H_2O$$
Water gas
Nickel oxide ($$NiO$$) is reduced by water gas to obtain nickel during its extraction.
Question 4
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Which one of the following methods is used in the concentration of sulphide ore ?

A
Froth floation

B
Smelting

C
Roasting

D
Leaching

Solution

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries, the single most important operation used for the recovery and upgrading of sulphide ores.
It is the process in which air bubbles are introduced into a mixture of finely divided ore or other material with water and a chemical that aids attachment of the bubbles to the particles of the desired material and its recovery as a froth.
Question 5
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The principle behind froth floatation is:

A
preferential wetting of ore and gangue particles.

B
difference is specific gravity of ore and gangue particles.

C
magnetic properties of ore and gangue.

D
electrical properties of gangue particles.

Solution

Froth flotation commences by comminution (that is, crushing and grinding), which is used to increase the surface area of the ore for subsequent processing and break the rocks into the desired mineral and gangue in a process known as liberation, which then has to be separated from the desired mineral. The ore is ground into a fine powder and mixed with water to form a slurry. The desired mineral is rendered hydrophobic by the addition of a surfactant or collector chemical. The particular chemical depends on which mineral is being refined. As an example, pine oil is used to extract copper. This slurry (more properly called the pulp) of hydrophobic mineral-bearing ore and hydrophilic gangue is then introduced to a water bath which is aerated, creating bubbles. The hydrophobic grains of mineral-bearing ore escape the water by attaching to the air bubbles, which rise to the surface, forming a foam or a scum (more properly called a froth). The froth is removed and the concentrated mineral is further refined.
Question 6
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Concentration by froth floatation is applicable for which of the following ores?

A
$$Al_2O_3$$

B
$$Te_3O_4$$

C
$$Te_2O_3.3H_2O$$

D
$$ZnS$$

Solution

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. it is mainly used for treatment of sulphide ores.
In some cases for example, sulphides ores of copper, zinc and lead concentration is brought by this method. In this method advantage is taken of the referential wetting of the ore by an oil. The finely ground ore is taken in a tank containing water and 1% of pine oil or terpentine oil.

A strong current of air is blown through the suspension, producing a heavy froth or foam on the surface.The metal sulphide is wetted by the oil but the gangues is not and the sulphide-oil mixture is carried to the surface by films of oil. The froth is skimmed off, the gangue settles down on the bottom or remains underneath the froth. Hence, it is applicable for $$ ZnS $$.
Question 7
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The zone refining process of metals is based on the principle of :

A
excess noble character of the liquid metal than that of impurity

B
lower melting point of the impurity than that of pure metal

C
greater solubility of impure metal than that of impurity

D
greater solubility of the impurities in the molten state than in the solid

Solution

Zone refining is particularly used when metals are required in high degree of purity. It is based on the principle that when an impure metal in a molten state is allowed to cool, only the metal crystallizes while the impurities remain present in the molten state (mass) or meltSo the zone refining process of metals is based on the principle ofGreater solubility of the impurities in the molten state than in the solid.
Hence option D is correct.
Question 8
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From the Ellingham graphs on carbon, which of the following statements is false?

A
$$CO_2$$ is more stable than $$CO$$ at less than $$983$$ K

B
$$CO$$ reduces $$Fe_2O_3$$ to $$Fe$$ at less than $$983$$ K

C
$$CO$$ is less stable than $$CO_2$$ at more than $$983$$ K

D
$$CO$$ reduces $$Fe_2O_3$$ to $$Fe$$ in the reduction zone of Blast furnace

Solution

$$\displaystyle CO_2 $$ is less stable than $$CO$$ at more than 983 K. At these temperatures, the $$\displaystyle \Delta G $$ value of formation of CO is more negative than the $$\displaystyle \Delta G $$ value of formation of $$\displaystyle CO_2 $$. More negative, the value of $$\displaystyle \Delta G $$, the greater is the tendency of the element to combine with oxygen.

Hence, the answer is option $$\text{C}$$
Question 9
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$$\Delta G^o$$ versus $$ T $$ plot in the Ellingham's diagram slopes downward for which of the reaction?

A
$$C+\dfrac{1}{2}O_2\rightarrow CO$$

B
$$CO+\dfrac{1}{2}O_2\rightarrow CO_2$$

C
$$2Ag+\dfrac{1}{2}O_2\rightarrow Ag_2O$$

D
$$Mg+\dfrac{1}{2}O_2\rightarrow MgO$$

Solution

$$C(s) + O_2 (g) → CO_2 (g)$$: Entropy of solids is negligible. So here one molecule of gas is resulting in one molecule of gas. Hence there is almost no net entropy. So there will be no slope, it is completely horizontal.

$$C (s)+ \frac{1}{2}O2 (g) → 2CO (g)$$: Here one mole of gas is giving you two moles of gas as products. So here the entropy will be positive. And as a result, this curve will go downwards.

Hence, the correct option is $$A$$
Question 10
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The reducing agent in thermite process is:

A
$$Al$$

B
$$Mg$$

C
$$Fe$$

D
$$Si$$

Solution

Hint:

The reduction of metal oxide by using aluminium as a reducing agent to obtain metal is termed a thermite reaction. It is an exothermic reaction.

Explanation:

Part 1:

When the mixture is heated, the reaction proceeds and as aluminium is more reactive than iron, aluminium forms stronger and stable bonds with oxygen than in comparison to iron.

Part 2:

Aluminium powder is used with ferric oxide because aluminium has more affinity towards oxygen and also reduces ferric oxide to elemental iron during the welding process.

Final Answer:

Hence, aluminium is used as a reducing agent in the thermite reduction reaction process.

Therefore, the correct answer is option $$A.$$

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General Principles and Processes of Isolation of Elements Test - 57

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General Principles and Processes of Isolation of Elements Test - 57

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Question 1

Na-ethyl xanthate is used as frother exclusively.

Levigation cannot be applied for sulphide in any condition.

Froth floatation can be applied for non-sulphide ore also using suitable activator.

Impurities like S and As are removed as elemental vapor in roasting.

Solution

Question 2

$$CO_2$$

$$SO_2$$

$$SO$$

$$NO_2$$

Solution

Question 3

$$NiO$$

$$ZnO$$

$$WO_{3}$$

$$Fe_{2}O_{3}$$

Solution

Question 4

Froth floation

Smelting

Roasting

Leaching

Solution

Question 5

preferential wetting of ore and gangue particles.

difference is specific gravity of ore and gangue particles.

magnetic properties of ore and gangue.

electrical properties of gangue particles.

Solution

Question 6

$$Al_2O_3$$

$$Te_3O_4$$

$$Te_2O_3.3H_2O$$

$$ZnS$$

Solution

Question 7

excess noble character of the liquid metal than that of impurity

lower melting point of the impurity than that of pure metal

greater solubility of impure metal than that of impurity

greater solubility of the impurities in the molten state than in the solid

Solution

Question 8

$$CO_2$$ is more stable than $$CO$$ at less than $$983$$ K

$$CO$$ reduces $$Fe_2O_3$$ to $$Fe$$ at less than $$983$$ K

$$CO$$ is less stable than $$CO_2$$ at more than $$983$$ K

$$CO$$ reduces $$Fe_2O_3$$ to $$Fe$$ in the reduction zone of Blast furnace

Solution

Question 9

$$C+\dfrac{1}{2}O_2\rightarrow CO$$

$$CO+\dfrac{1}{2}O_2\rightarrow CO_2$$

$$2Ag+\dfrac{1}{2}O_2\rightarrow Ag_2O$$

$$Mg+\dfrac{1}{2}O_2\rightarrow MgO$$

Solution

Question 10

$$Al$$

$$Mg$$

$$Fe$$

$$Si$$

Solution

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