General Principles and Processes of Isolation of Elements Test

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General Principles and Processes of Isolation of Elements Test - 58

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Weekly Quiz Competition

Question 1
1 / -0

The correct statements with respect to Ellingham's diagram among the following are
(I) Magnesium reduces aluminium oxide below 1700 K
(II) Aluminium reduces magnesium oxide above 1700 K
(III) Aluminium reduces magnesium oxide below 1700 K
(IV) Magnesium reduces aluminium oxide above 1700 K

A
I & II

B
II & III

C
III & IV

D
II, III & IV

Solution

The correct statements with respect to Ellingham's diagram are I & II
(I) Magnesium reduces aluminium oxide below 1700 K.
Below 1700 K, $$\displaystyle \Delta G^o$$ for the reaction $$\displaystyle 2Mg + O_2 \rightarrow 2MgO$$ is more negative than $$\displaystyle \Delta G^o$$ for the reaction $$\displaystyle \dfrac {4}{3} Al +O_2 \rightarrow \dfrac {2}{3}Al_2O_3$$

(II) Aluminium reduces magnesium oxide above 1700 K
Above 1700 K, $$\displaystyle \Delta G^o$$ for the reaction $$\displaystyle 2Mg + O_2 \rightarrow 2MgO$$ is less negative than $$\displaystyle \Delta G^o$$ for the reaction $$\displaystyle \dfrac {4}{3} Al +O_2 \rightarrow \dfrac {2}{3}Al_2O_3$$
More negative the value of $$\displaystyle \Delta G^o$$, the greater is the tendency of the element to combine with oxygen.
Hence, the option (A) is the correct answer.
Question 2
1 / -0

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

A
$$180\ kg$$

B
$$270\ kg$$

C
$$540\ kg$$

D
$$90\ kg$$

Solution

In hall and Heroult process

$$2{ Al }_{ 2 }{ O }_{ 3 }\longrightarrow 4Al+3{ O }_{ 2 }$$

$$4C+3{ O }_{ 2 }\longrightarrow 2{ CO }_{ 2 }+2CO\uparrow $$

Only for removal of $${CO}_{2}$$ following equation is possible

$$2{ Al }_{ 2 }{ O }_{ 3 }+\underset { 3\times 12=36 }{ 3C } \longrightarrow \underset { 4\times 27=108 }{ 4Al } +3{ CO }_{ 2 }\quad $$

$$\because$$ For $$108kg$$ of $$Al$$, $$36 kg$$ of $$C$$ is required in above reaction

$$\therefore$$ For $$270kg$$ of $$Al$$ require amount of $$C$$

$$=\cfrac { 36 }{ 108 } \times 270=90kg$$

Hence, the correct option is $$D$$
Question 3
1 / -0

Copper, a metal known from ancient times, has many uses, some of which are mentioned here. Can you pick the false one?

A
As an alloy in high-speed drills

B
In brass utensils and bronze statues

C
In electric motor coils

D
In tapes and water connections

Solution

Copper is a good conductor of heat. When it is used in speed drills, because of friction, heat develops and it melts. Therefore, it is not used in speed drills.
Question 4
1 / -0

Pyrolusite is:

A
a sulphide ore of $$Mn$$

B
an oxide ore of $$Mn$$

C
a carbide ore of $$P$$

D
a chloride ore of $$Zn$$

Solution

Out of many minerals in which a metal may be found, only a few are viable to be used as source of that metal. Such minerals are known as ores.
Not all elements exists in pure states. Some elements exist in combined states.Among them the viable ones are there ores and the pure metal is obtained after undergoing various metallurgical processes.
Pyrolusite-($$MnO_2$$) is an oxide ore of Manganese.
Question 5
1 / -0

Which of the following ores are concentrated by Froth Flotation.

A
Oxide ores

B
Chloride ores

C
Sulphide ores

D
Nitride ores

Solution

Sulphide ores are concentrated by Froth Flotation.
Galena (PbS), zinc blende (ZnS) and copper pyrites $$ \displaystyle (CuFeS_2)$$ are concentrated by Froth Flotation.
Question 6
1 / -0

The reduction of an oxide by aluminium is called:

A
Kroll's process

B
Van Arkel process

C
Ellingham process

D
Goldschmidt's aluminothermite process

Solution

In Goldschmidt's alumino thermite process, is used when a high temperature is needed for carbon to reduce an oxide. In this process a large amount of energy $$(1675\ kJ\ mol^{-1})$$ is liberated on oxidation to $$Al_{2}O_{3}$$.
$$3Mn_{3}O_{4} + 8Al\rightarrow 9Mn + 4Al_{2}O_{3}$$

$$B_{2}O_{3} + 2Al\rightarrow 2B + Al_{2}O_{3}$$

$$Cr_{2}O_{3} + 2Al\rightarrow 2Cr + Al_{2}O_{3}$$
Question 7
1 / -0

Impurities of sulphur, silicon, and phosphorus can be removed from cast iron by adding:

A
carbon which reduces the impurities

B
water which dissolves the impurities

C
limestone which changes impurities into oxides and pass into slag

D
iron oxide which reacts with impurities by forming slag

Solution

Flux is added to remove impurities as slag. So impurities like Sulphur, Silicon and Phosphorous are removed from case Iron by adding flux. Here flux is $$CaC{ O }_{ 3 }$$
Question 8
1 / -0

For the reduction of $$FeO$$ with $$C$$ at the temperature corresponding to $$(D)$$, which of the following statements is correct?

A
Carbon reduces $$FeO$$ below the temperature at point (D)

B
$$\triangle G^0$$ value for overall reduction with $$CO$$ is zero

C
$$\triangle G^0$$ value for the reaction at point (D) is positive

D
Below point (D), for the metal exists in molten state

Solution

At the point 'D', both the curves of oxidation of Fe and oxidation of CO intersect, therefore at this point, $$\triangle G°$$ value for the overall reduction of FeO to Fe with CO is zero.
Question 9
1 / -0

The mineral carnallite contains __(i)___and __(ii)____metals. ____(iii)____ is purified by cupellation and ____(iv)_____is purified by distillation.

A
(i) -calcium , (ii)- zinc, (iii)- mercury, (iv)- tin

B
(i)- calcium, (ii)- magnesium, (iii)- zinc, (iv)- lead

C
(i)- potassium, (ii)- calcium, (iii)- copper, (iv)- mercury

D
(i)- magnesium, (ii)-potassium, (iii)- silver, (iv)- mercury

Solution

Carnallite $$\rightarrow KCl.Mg{ Cl }_{ 2 }.6{ H }_{ 2 }O$$. It contains $$Mg$$ and $$K$$. Silver is purified by cupellation. Because of its low boiling point, mercury is purified with distillation.
Question 10
1 / -0

Which of the following statements is correct according to the basic concept of thermodynamics which govern the feasibility of a metallurgical process?

A
When the value of $$\triangle $$G is positive for the equation $$\triangle $$G=$$\triangle $$H-T$$\triangle $$S, the reaction will proceed.

B
If reactants and products of two reactions are put together and net $$\triangle $$G is -ve, the overall reaction will occur.

C
On increasing the temperature, the value of $$\triangle $$G becomes +ve.

D
Feasibility of thermal oxidation of an ore can be established by Ellingham diagram in which a straight line shows the reduction reaction will proceed.
Solution
The change in Gibbs energy, $$\Delta G$$ for any process at any specified temperature, is described by the equation:
$$\Delta G=\Delta H -T\Delta S$$
where $$\Delta H$$ is the enthalpy change and $$\Delta S$$ is the entropy change for the process.
When the value of $$\Delta G$$ is negative in equation only then the reaction will proceed.$$\Delta G$$ can become negative in the following situations:
1. If $$\Delta S$$ is positive, on increasing the temperature (T), the value of
$$T\Delta S$$ increases so that $$\Delta H$$ < $$T\Delta S$$. In this situation, $$\Delta G$$ will become negative on increasing temperature.
2. If the coupling of the two reactions, i.e. reduction and oxidation, results in a negative value of $$\Delta G$$ for the overall reaction, the final reaction becomes feasible.
Hence, option $$B$$ is the correct answer.

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General Principles and Processes of Isolation of Elements Test - 58

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General Principles and Processes of Isolation of Elements Test - 58

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Question 1

I & II

II & III

III & IV

II, III & IV

Solution

Question 2

$$180\ kg$$

$$270\ kg$$

$$540\ kg$$

$$90\ kg$$

Solution

Question 3

As an alloy in high-speed drills

In brass utensils and bronze statues

In electric motor coils

In tapes and water connections

Solution

Question 4

a sulphide ore of $$Mn$$

an oxide ore of $$Mn$$

a carbide ore of $$P$$

a chloride ore of $$Zn$$

Solution

Question 5

Oxide ores

Chloride ores

Sulphide ores

Nitride ores

Solution

Question 6

Kroll's process

Van Arkel process

Ellingham process

Goldschmidt's aluminothermite process

Solution

Question 7

carbon which reduces the impurities

water which dissolves the impurities

limestone which changes impurities into oxides and pass into slag

iron oxide which reacts with impurities by forming slag

Solution

Question 8

Carbon reduces $$FeO$$ below the temperature at point (D)

$$\triangle G^0$$ value for overall reduction with $$CO$$ is zero

$$\triangle G^0$$ value for the reaction at point (D) is positive

Below point (D), for the metal exists in molten state

Solution

Question 9

(i) -calcium , (ii)- zinc, (iii)- mercury, (iv)- tin

(i)- calcium, (ii)- magnesium, (iii)- zinc, (iv)- lead

(i)- potassium, (ii)- calcium, (iii)- copper, (iv)- mercury

(i)- magnesium, (ii)-potassium, (iii)- silver, (iv)- mercury

Solution

Question 10

When the value of $$\triangle $$G is positive for the equation $$\triangle $$G=$$\triangle $$H-T$$\triangle $$S, the reaction will proceed.

If reactants and products of two reactions are put together and net $$\triangle $$G is -ve, the overall reaction will occur.

On increasing the temperature, the value of $$\triangle $$G becomes +ve.

Feasibility of thermal oxidation of an ore can be established by Ellingham diagram in which a straight line shows the reduction reaction will proceed.

Solution

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