General Principles and Processes of Isolation of Elements Test

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General Principles and Processes of Isolation of Elements Test - 62

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Weekly Quiz Competition

Question 1
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Boron can be obtained by various methods but not by:

A
Pyrolysis of $$BI_3$$ (Van Arkel)

B
Reducing $$BCl_3$$ with $$H_2$$

C
Electrolysis of fused $$BCl_3$$

D
Oxidation of $$B_2O_3$$

Solution
Question 2
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Directions For Questions

Lead obtained from galena ore (PbS) by air reduction or carbon reduction process contains base metal (Cu, Bi, Sn, As) as impurities it is due to the presence of these impurities that lead becomes hard and brittle.

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Ag can be obtained from purified Zn-Ag alloy by:

A
Distillation

B
Poling

C
Liquation

D
Reduction

Solution
Question 3
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Directions For Questions

Lead obtained from galena ore (PbS) by air reduction or carbon reduction process contains base metal (Cu, Bi, Sn, As) as impurities it is due to the presence of these impurities that lead becomes hard and brittle.

...view full instructions

Zn-Ag alloy formed in the upper layer of molten lead is skimmed off from the surface of the molten lead by perforated ladles. This alloy contains lead as impurity. This impurity of Pb is removed by:

A
Distillation process

B
Cupellation

C
Liquation

D
Bett's electrolysis

Solution
Question 4
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The ore having two different metal atoms is:

A
Hematite

B
Galena

C
Magnetite

D
Copper pyrites

Solution
Question 5
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Which of the following is incorrect on the basis of the above Ellingham diagram for carbon?

A
Up to $$710^0C$$, the reaction of formation of $$CO_2$$ is energetically more favourable, but above $$710^0C$$, the formation of CO is preferred

B
In principle, carbon can be used to reduce any metal oxide at a sufficiently high temperature

C
$$\Delta S (C_{(s)} + \frac{1}{2}O_{2(g)} \rightarrow CO_{(g)} \ < \Delta S (C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)})$$

D
Carbon reduces many oxides at elevated temperature because $$\Delta G^0$$ vs temperature line has a negative slope
Question 6
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Tin is not refined by:

A
Liquation

B
Zone refining

C
Poling

D
Any of these

Solution

Poling is a [metallurgical] method employed in the purification of copper which contains copper oxide as an impurity and also in the purification of tin ("Sn") which contains tin oxide (stannic oxide or $$SnO_{2}$$) as an impurity. It was the use of these greenwood poles gave rise to the term "poling."

Liquation is suitable for metals with low melting points for example, tin. In this process, we heat the impure metal and then we let it flow on a sloped surface. The impurities will remain behind and the pure metal will collect at the bottom of the slope.

Zone refining is a special method we use to purify metals. It was the invention of William Pfann. It purifies metals to a very high degree. A rod of impure metal is placed in a container which we fill with inert gas. Then we place a circular heater around the rod at the top.

The melting point of tin is low. So zone refining is not suitable for Tin.

Hence, option B is correct.
Question 7
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Directions For Questions

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.

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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.

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

(c) Froth floatation can also 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 so their volatile oxides $$SO_2$$ and $$As_2O_3$$ respectively.
Question 8
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Find out A:

A
$$Cu_2S$$

B
$$CuFeS_2$$

C
$$FeS_2$$

D
$$Fe_3O_4$$

Solution
Question 9
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Directions For Questions

These equilibria can be discussed in terms of thermodynamic functions.
For the reaction :
(i) $$\displaystyle M_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow MO_(s)$$
(ii) $$\displaystyle \frac{1}{2} C_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow \frac{1}{2} CO_{2(g)}$$
(iii) $$\displaystyle C_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{(g)}$$
(iii) $$\displaystyle CO_{(g)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{2(g)}$$
The temperature dependence of $$\Delta \mathring{G}$$ of reaction $$(i)$$ to $$(iv)$$ is shown in the given diagram. This is known as Ellingham diagram. With the help of Ellingham diagram, one can easily predict the most suitable reducing agent for the reduction of metal oxides.

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$$Al_2O_3$$ can be reduced by carbon at a temperature of :

A
$$30^0C$$

B
$$500^0C$$

C
$$2000^0C$$

D
$$>2500^0C$$

Solution

Explanation:
An Ellingham diagram is a graph showing the temperature dependence of the stability for compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides and sulfides. These diagrams were first constructed by Harold Ellingham in 1944.
Carbon cannot be used in the reduction of $$Al_2O_3$$ in metallurgy. Aluminum oxide is a very stable oxide and lies below the oxidation line of carbon in Ellingham Diagram. Hence, $$Al_2O_3$$ cannot be reduced by carbon as it is energetically not favorable.
A very high temperature is required. $$Al_2O_3$$ can be reduced by carbon at a temperature $$>2500^{\circ}C$$ as it is a stable oxide.
Option D is the correct answer.
Question 10
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Froth floatation process is based on :

A
Specific gravity of the ore particles

B
Magnetic properties of the ore particles

C
Wetting properties of the ore particles

D
Electric properties of the ore particles

Solution