General Principles and Processes of Isolation of Elements MCQs

Elements can be found in nature in either a coupled or a free state depending on their chemical composition. There are only a few of them that occur in free state or native. Copper, silver, gold, platinum, and other platinum group metals are examples of metals that occur naturally in their free state. Carbon, sulphur, nitrogen, oxygen, and noble gases are examples of non-metals that can exist in their free state. The presence of an element in nature, whether in a coupled condition or in a free state, is dependent on a number of fundamental elements that must be investigated. On the basis of spectral study of distant stars, scientists have calculated the amount of elements in the universe. There is a remarkable degree of consistency in this regard, according to the results of the research.

1. In the equation, 4M + 8CN^– + H₂O + O₂ → 4[M(CN)₂]^– + 4OH^– , the metal M is

1. 1. copper

   2. iron

   3. gold

   4. Zinc

Answer: (C)The Mac-Arthur Forrest cyanide procedure, described above, is used for the extraction of precious metals such as gold and silver.

2. Heating ore with carbon in the absence of air is known as:

1. 1. reduction

   2. carbon-reduction

   3. smelting

   4. Roasting

Answer: (C) Calcination is the process of heating ore in the absence of air to temperatures below its melting point. It is possible to obtain a huge number of organic compounds as well as some inorganic compounds from coal when it is burned without the presence of oxygen. Destructive distillation of coal is the name given to this procedure. It is possible to obtain coal tar and coal gas with this technique.

3. In the extraction of copper from sulphide ore, the metal is formed by reduction of Cu₂O with

1. 1. FeS

   2. CO

   3. Cu₂S

   4. SO₂

Answer: (C)Copper is extracted from sulphide ore by simply heating the ore in the presence of oxygen. Copper sulphide is heated in the presence of oxygen in order to transform it into copper oxide. In order to make pure copper metal, copper oxide is combined with sulphite. In a furnace or set of furnaces, the concentrated ore is subjected to intense heating with silicon dioxide (silica) and air or oxygen to extract the valuable minerals. The copper(II) ions in chalcopyrite are reduced to copper(I) sulphide during the reduction process (which is reduced further to copper metal in the final stage).

4. The method of zone refining of metals is based upon the principle of

1. 1. greater solubility of the impurity in molten state than in solid

   2. greater mobility of pure metal than impurity

   3. higher melting point of impurity than that of pure metal.

   4. greater noble character of solid metal than that of the impurity

Answer: (A) Zoning refinement is a technique for the purification of crystalline materials, particularly metals, in which a molten region travels through the material to be refined, picks up impurities at its advancing edge, and then allows the purified part to recrystallize at its opposing edge. Zone refining is also known as zone melting. Zoning is a technique for improving the purity of metals, and it is based on the premise of greater solubility of impurities in molten metal as opposed to solid metal. This process is used to purify elements such as silicon, germanium, gallium, and other semiconductor elements.

5. Cassiterite is the ore of which metal?

1. 1. Mn

   2. Sb

   3. Sn

   4. Ni

Answer: (C) Cassiterite is the primary mineral from which tin may be extracted (Gladwell et al., 1981). According to Miller et al. (1994), tin is required for the production of solder on printed circuit boards (PCBs) and in packages. Cassiterite is a tin oxide mineral with a chemical composition of SnO₂ and is found in the earth’s crust. It is the world’s most important source of tin, with cassiterite mining accounting for the majority of the world’s tin production. Worldwide, small amounts of primary cassiterite can be found in igneous and metamorphic rocks of varying compositions.

6. In electrorefining of copper some gold is produced as:

1. 1. cathode mud

   2. anode mud

   3. cathode deposit

   4. anode deposit

Answer: (B) Impurities such as iron, nickel, and zinc dissolve within the solution, whereas impurities such as gold, silver, and platinum deposit as anode mud beneath the anode electrode. It is reasonable to conclude that gold (Au) is deposited as anode mud beneath the anode electrode. Electrorefining is the process of electrochemically dissolving copper from impure copper anodes into an electrolyte containing CuSO₄ and H₂SO₄ and then electrochemically depositing pure copper from the electrolyte onto stainless steel or copper cathodes, a process known as electrochemical deposition. The procedure is an ongoing one.

7. In the electrolytic method of obtaining aluminium from purified bauxite, cryolite is added to the charge in order to:

1. 1. lower the melting point of bauxite

   2. dissolve bauxite and render it a conductor of electricity

   3. protect aluminium produced from oxygen

   4. minimise the heat loss due to radiation

Answer: (B)Cryolite is added to the charge in the electrolytic process of generating aluminium from refined bauxite in order to dissolve the bauxite and make it a conductor of electricity, which is used to produce aluminium.

8. The purest form of iron is:

1. 1. cast iron

   2. pig iron

   3. wrought iron

   4. steel

Answer: (C) Wrought iron is the purest form of iron that can be found. The carbon percentage in pure carbon steel (iron-carbon alloys) ranges between 0.002 percent and 2.14 percent by weight, depending on the steel type. Pure iron is extremely fragile, ductile, and brittle due to a lack of carbon in its composition. A brittle alloy known as pig iron is formed of carbon concentrations that are higher than those found in steel, making it more brittle. Cast iron is made by pouring molten iron into a mould and allowing it to cool down. Wrought iron is iron that has been melted and then handled with special equipment once it has cooled. In fact, the phrase “wrought” is derived from the past participle of the verb “worked,” which means “to work hard.”

9. During the process of electrolytic refining of copper, some metals present as impurity settle as ‘anode mud’. These are:

1. 1. Pb and Zn

   2. Sn and Ag

   3. Fe and Ni

   4. Ag and Au

Answer: (D)

Explanation: During copper electrolytic refining. Antimony, selenium, tellurium, silver, gold, and platinum are all present in the anode mud from the blister copper deposit.

10. Extraction of zinc from zinc blende is achieved by

1. 1. electrolytic reduction

   2. roasting followed by reduction with carbon

   3. roasting followed by reduction with another metal

   4. roasting followed by self-reduction

Answer: (B)

Explanation: Zinc is extracted from zinc blende by roasting it first and then reducing it with carbon.

Roasting:

2Zns + 3O₂ → 2ZnO + 2SO₂

Reduction with Carbon:

ZnO + C → Zn + CO

The temperature for the above is greater than 1270K.

Conclusion

The methods and isolation of metals from their sources are discussed in this chapter. Metals are always extracted from their mineral sources. Mining is used to collect these ores, which are present in the earth’s crust. These ores include gangue, which is a type of impurity. Several procedures are required to obtain metals in their pure state.