General Principles and Processes of Isolation of Elements Test

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General Principles and Processes of Isolation of Elements Test - 52

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Weekly Quiz Competition

Question 1
1 / -0

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

A
$$90\ kg$$

B
$$540\ kg$$

C
$$180\ kg$$

D
$$270\ kg$$

Solution

The reaction is : $$ 2Al_{2}O_{3} +3C \rightarrow 4Al+3CO_{2} $$

Molar mass of aluminium is $$27\ gmol^{-1}$$

Molar mass of carbon is $$ 12\ gmol^{-1}$$

Carbon required is $$ \dfrac{12 \times 3 \times 270}{4 \times 27}=90Kg$$

Option A is correct.
Question 2
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Choose the correct statement(s) for froth flotation process, which is used for the concentration of sulphide ore.
a) It is based on the difference in the ability of different minerals to become wet.
b) It uses sodium ethyl xanthate, $$C_{2}H_{5}OCS_{2}Na$$ as collector.
c) It uses $$NaCN$$ as a depressant in the mixture of $$ZnS$$ and $$PbS$$, where $$ZnS$$ forms soluble complex and $$PbS$$ forms froth.

A
Only (a) and (b) are correct

B
Only (b) and (c) are correct

C
Only (a) and (c) are correct

D
All statements are correct

Solution

In some sulphide ores of copper, zinc and lead, the concentration is brought by the froth flotation process. In this method, the advantage is taken of the preferential wetting of the ore by an oil. The finely ground ore is taken in a tank containing water and 1% of pine oil or turpentine oil.
Collectors (e.g., pine oils, fatty acids, xanthates, etc.) enhance the non-wettability of the mineral particles and froth stabilisers (e. g., cresols, aniline) stabilise the froth.
Sometimes, it is possible to separate two sulphide ores by adjusting the proportion of oil to water or by using ‘depressants’. For example, in the case of an ore containing ZnS and PbS, the depressant used is NaCN. It selectively prevents ZnS from coming to the froth but allows PbS to come with the froth.
Option D is correct.
Question 3
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Select the correct statement for electrolysis of $$Al_2O_3$$ by Hall-Heroult process.

A
Cryolite $$Na_3[AlF_6]$$ lowers the melting point of $$Al_2O_3$$ and increases its electrical conductivity.

B
Al is obtained at cathode and probably $$CO_2$$ at anode.

C
Both of the above statements are correct.

D
None of the above statements are correct.

Solution

In the extraction of aluminium by electrolytic process, alumina $$Al_2O_3$$ is used along with fluorspar and cryolite.
Cryolite reduces the melting temperature of the mixture and also acts as a solvent and helps dissolve $$Al_2O_3$$.
Cryolite: $$Na_3[AlF_6]$$
$$Na_{3}[AlF_{6}]\rightarrow 3NaF+AlF_{3}$$
$$NaF$$ and $$AlF_3$$, both are ionic compounds, and ionise to give ions. This increases the electrical conductivity and lowers the melting point of $$Al_2O_3$$.
At cathode: $$Al^{3+} +3e^-\rightarrow Al$$
At anode: $$C(s) + O^{2-} (melt) \rightarrow CO (g) +2e^-$$
$$C(s) + 2O^{2-} (melt) \rightarrow CO_2 (g) + 4e^-$$
Question 4
1 / -0

The main function of frothers is to _________________.

A
stick to the ore and take it to the top

B
convert the insoluble ore into soluble part

C
make the ore hydrophobic

D
none of the above

Solution

In the froth floatation process, oil is used as a frothing agent, also called as frothers. It reduces surface tension and helps to stablise froth. So, the main task of frothers is to stick to the ore and then take it to the top.
Question 5
1 / -0

Froth floatation process is used for the concentration of sulphide ores. This process is an illustration of the practical application of:

A
adsorption

B
absorption

C
sedimentation

D
coagulation

Solution

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries.

It has been described as the single most important operation used for the recovery and upgrading of sulfide ores.

Froth floatation process is used for the concentration of sulphide ores. This is an illustration of the practical application of adsorption, as the sulphide ores get preferentially adsorbed over the impurities.

Option A is correct.
Question 6
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Which of the following reaction is a part of Hall's process?

A
$$Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$$

B
$$Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3$$

C
$$AlN + 3H_2O \rightarrow Al(OH)_3 + NH_3$$

D
$$Al_2O_3. 2H_2O + 2Na_2CO_3 \rightarrow 2NaAlO_2 + CO_2 + 2H_2O$$

Solution

Hall's process is used for the extraction of Aluminum from Alumina.

The reaction involved in the Hall's process is as follows :

$$Al_2O_3. 2H_2O + 2Na_2CO_3 \rightarrow 2NaAlO_2 + CO_2 + 2H_2O$$

Option D is correct.
Question 7
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Directions For Questions

The Ellingham diagram for zinc, magnesium and carbon converting into corresponding oxides is shown above. In the diagram, the points shown are melting and boiling points of zinc and magnesium metals. $$\Delta G^o$$ is a function of temperature for some reactions of extractive metallurgy.

...view full instructions

At what temperature do zinc and carbon have equal affinity for oxygen?

A
$$1000^oC$$

B
$$1500^oC$$

C
$$500^oC$$

D
$$1200^oC$$

Solution

As both oxides of zinc and carbon, i.e., $$ZnO\: \& \: CO$$ met at $$1000^oC$$ in graph, so at this temperature, both carbon and zinc have equal affinity with oxygen.
Question 8
1 / -0

Concentration of which of the following ore is carried out by froth floatation process?

A
Bauxite

B
Chalcocite

C
Haematite

D
Calamine

Solution

Froth flotation process is selectively used for separating hydrophobic and hydrophilic substances. Chalcocite ($$Cu_2S$$) is a sulphide ore and sulphide ores are concentrated by froth floatation.
Question 9
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Which of the following reactions does not occur in Bessemer's converter?

A
$$2Cu_{2}S+5O_{2}\rightarrow 2CuSO_{4}+2CuO$$

B
$$2Cu_{2}S+3O_{2}\rightarrow 2Cu_{2}O+2SO_{2}\uparrow $$

C
$$2CuFeS_{2}+O_{2}\rightarrow Cu_{2}S+2FeS+SO$$

D
$$FeO+SiO_2\rightarrow FeSiO_3$$

Solution

In the extraction of copper, following reactions occur in Bessemer converter:

$$2Cu_{2}S+3O_{2}\rightarrow 2CuO+2SO_{2}$$
$$Cu_{2}S+2Cu_{2}O\rightarrow 6Cu+SO_{2}$$
$$2Cu_2S +5O_2 \rightarrow 2CuSO_4 + 2 CuO$$
$$2Cu_2S +Cu_2SO_4 \rightarrow 4Cu + 2 SO_2$$
$$FeO+SiO_2 \rightarrow FeSiO_3$$

Roasting takes place in a furnace in the presence of a current of air. In this process, $$2CuFeS_{2}+O_{2}\rightarrow Cu_{2}S+2FeS+SO$$, reaction takes place.
Question 10
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Which of the following is not correctly matched with respect to the processes involved in the extractive metallurgy of the respective metal?

A
$$Al_2O_3.2H_2O\rightarrow Al$$: Leaching, precipitation, calcination and electrolytic reduction (molten state)

B
$$Ag_2S\rightarrow Ag$$: Leaching and displacement method

C
$$PbS\rightarrow Pb$$: Froth flotation process, roasting and self reduction

D
$$KCl.MgCl_2.6H_2O\rightarrow Mg$$: Dehydration by simple heating and electrolytic reduction in aqueous phase

Solution

A) Extraction of $$Al$$ from its ore follows these steps:
Leaching, precipitation, calcination and electrolytic reduction (molten state)
$$Al_2O_3(s)+3H_2O(l)+2NaOH(aq)\xrightarrow {Leaching} 2Na[Al(OH)_4](aq)$$

$$2Na[Al(OH)_4](aq)+CO_2(g)\rightarrow Al_2O_3.xH_2O(s)+2NaHCO_3(aq)$$

$$Al_2O_3.xH_2O(s)\xrightarrow [Calcination]{1470K} Al_2O_3(s)+xH_2O(g)$$

Electrolytic reduction of molten pure $$Al_2O_3$$ is mixed with $$Na_2AlF_6$$ or $$CaF_2$$

This method is known as Hall-Heroult process
$$Cathode: Al^{3+}(melt)+3e^-\rightarrow Al(l)$$

$$Anode: C(s)+O^{2-}(melt)\rightarrow CO(g)+2e^-$$
$$C(s)+2O^{2-}(melt)\rightarrow CO_2(g)+4e^-$$

B) In case of $$Ag$$, extraction follows leaching and displacement method as:
Leaching:
$$Ag_2S+4NaCN\rightleftharpoons 2Na[Ag(CN)_2]+Na_2S$$
$$Na_2S+2O_2\rightarrow Na_2SO_4$$

Displacement by zinc in aqueous solution:
$$2Na[Ag(CN)_2]+Zn\rightarrow Na_2[Zn(CN)_4]+2Ag\downarrow$$

C) Extraction of $$Cu$$ follows these as:
Roasting:
$$2PbS+3O_2\xrightarrow {\Delta} 2PbO+2SO_2$$

Self reduction:
$$2PbO+PbS\rightarrow 2Pb+SO_2$$

D) Extraction of $$Mg$$ follows:
Calcination:
$$MgCl_2.6H_2O\xrightarrow [Dry HCl(g)]{\Delta (calcination)} MgCl_2+5H_2O$$

It is not made anhydrous by simple heating because it gets hydrolysed
$$MgCl_2.6H_2O\xrightarrow {\Delta} MgO.5H_2O+2HCl$$

Electrolytic reduction:
Electrolytic reduction of molten anhydrous carnalite.
$$MgCl_2\rightleftharpoons Mg^{2+}+2Cl^-$$

At cathode: $$Mg^{2+}+2e^-\rightarrow Mg$$ (99% pure);

At anode: $$2Cl^-\rightarrow Cl_2+2e^-$$

Option D represents the incorrect statement.

Ans-option D

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General Principles and Processes of Isolation of Elements Test - 52

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General Principles and Processes of Isolation of Elements Test - 52

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Question 1

$$90\ kg$$

$$540\ kg$$

$$180\ kg$$

$$270\ kg$$

Solution

Question 2

Only (a) and (b) are correct

Only (b) and (c) are correct

Only (a) and (c) are correct

All statements are correct

Solution

Question 3

Cryolite $$Na_3[AlF_6]$$ lowers the melting point of $$Al_2O_3$$ and increases its electrical conductivity.

Al is obtained at cathode and probably $$CO_2$$ at anode.

Both of the above statements are correct.

None of the above statements are correct.

Solution

Question 4

stick to the ore and take it to the top

convert the insoluble ore into soluble part

make the ore hydrophobic

none of the above

Solution

Question 5

adsorption

absorption

sedimentation

coagulation

Solution

Question 6

$$Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$$

$$Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3$$

$$AlN + 3H_2O \rightarrow Al(OH)_3 + NH_3$$

$$Al_2O_3. 2H_2O + 2Na_2CO_3 \rightarrow 2NaAlO_2 + CO_2 + 2H_2O$$

Solution

Question 7

$$1000^oC$$

$$1500^oC$$

$$500^oC$$

$$1200^oC$$

Solution

Question 8

Bauxite

Chalcocite

Haematite

Calamine

Solution

Question 9

$$2Cu_{2}S+5O_{2}\rightarrow 2CuSO_{4}+2CuO$$

$$2Cu_{2}S+3O_{2}\rightarrow 2Cu_{2}O+2SO_{2}\uparrow $$

$$2CuFeS_{2}+O_{2}\rightarrow Cu_{2}S+2FeS+SO$$

$$FeO+SiO_2\rightarrow FeSiO_3$$

Solution

Question 10

$$Al_2O_3.2H_2O\rightarrow Al$$: Leaching, precipitation, calcination and electrolytic reduction (molten state)

$$Ag_2S\rightarrow Ag$$: Leaching and displacement method

$$PbS\rightarrow Pb$$: Froth flotation process, roasting and self reduction

$$KCl.MgCl_2.6H_2O\rightarrow Mg$$: Dehydration by simple heating and electrolytic reduction in aqueous phase

Solution

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