General Principles And Process of Isolation of Elements MCQ Quiz - Objective Question with Answer for General Principles And Process of Isolation of Elements - Download Free PDF

CONCEPT:

Froth Floatation Method

• The froth flotation method is a process used for the concentration of ores, particularly sulfide ores, by separating valuable minerals from the gangue material (waste material).
• A rotating paddle is used to create bubbles, which attach to the hydrophobic particles in the slurry. These bubbles rise to the surface, forming a froth layer, and the valuable minerals are collected from the froth.
• The role of the rotating paddle is to stir the mixture and introduce air into the system, not to drive air out of it.
  

Iron Pyrites and Iron Extraction

• Iron pyrites (FeS₂) are not generally used for the extraction of iron because of environmental concerns, as burning iron pyrites releases sulfur dioxide (SO₂), a toxic gas.
• Iron pyrites are typically avoided in iron extraction because they contribute to pollution and are less efficient compared to other iron ores like hematite (Fe₂O₃).

EXPLANATION:

• In the froth flotation method, the rotating paddle helps introduce air into the pulp, creating bubbles, rather than driving air out of it. Thus, Statement I is incorrect.
• Iron pyrites are avoided for the extraction of iron because of the environmental hazards associated with sulfur dioxide emissions. This makes Statement II correct.

Therefore, the correct answer is: Statement I is false but Statement II is true.

EXPLANATION:

Extraction of Copper from Copper Pyrites (CuFeS₂)

• The extraction involves partial roasting of copper pyrites, followed by self-reduction and slag formation.
• During the process, the following key reactions occur:
  • Partial roasting:

    2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂

  • Iron sulfide oxidation:

    2FeS + 3O₂ → 2FeO + 2SO₂

  • Formation of slag with silica:

    FeO + SiO₂ → FeSiO₃ (slag)

• Slag helps in the removal of iron impurities as iron silicate.
•  Occurs during partial roasting of copper sulfide → Correct
• FeS is oxidized to FeO and SO₂ →Correct
• Formation of CaSiO₃ (calcium silicate) → Incorrecct
  • This reaction is characteristic of iron extraction using lime (CaO), not copper.
•  FeO reacts with SiO₂ to form iron silicate → Correct

Therefore, the correct answer isCaO + SiO₂ → CaSiO₃ does not occur in copper extraction.

CONCEPT:

Van Arkel Method (Iodide Process)

• This method is used to purify transition metals like Ti and Zr.
• It involves converting impure metal to a volatile metal iodide, which then decomposes to give pure metal.
• The reaction steps:
  1. Ti (impure) + I₂ → TiI_x (volatile) [at moderate temperature]
  2. TiI_x → Ti (pure) + I₂ [at high temperature over a hot filament]
• The actual iodide formed is Titanium(IV) iodide (TiI₄).
• This is because Ti commonly shows a +4 oxidation state in its halides.

EXPLANATION:

• From the second image:

• This confirms that the iodide formed is TiI₄, so x = 4.

Therefore, the value of x = 4.

CONCEPT:

Abundance of Elements on Earth

• The abundance of elements can be considered in the context of the Earth's crust, atmosphere, and overall composition.
• Oxygen is the most abundant element in the Earth's crust and is also highly prevalent in the atmosphere and oceans, making it the overall most abundant element on Earth.
• Nitrogen is highly abundant in the atmosphere but less so in the Earth's crust and overall composition.
• Carbon and hydrogen are essential for life and are abundant in organic compounds but are not the most abundant elements overall.

EXPLANATION:

• Considering the overall abundance of elements in the Earth's crust, oceans, and atmosphere:
  • Oxygen (O) comprises about 46.6% of the Earth's crust by weight, 28% of the Earth's atmosphere as O2, and is a major component of water (H₂O) in the oceans.
  • Nitrogen (N) is abundant in the atmosphere (about 78% by volume) but not as prevalent in the Earth's crust and oceans.
  • Carbon (C) and Hydrogen (H) are present in significant amounts in organic compounds but are not the most abundant elements overall.

Therefore, the most abundant element on Earth is oxygen (O).

CONCEPT:

Copper Ores and Their Chemical Composition

• Copper is commonly found in nature in the form of various ores, from which it is extracted.
• The most important and abundant copper ore is Chalcopyrite (CuFeS₂).
• It is a sulfide mineral and the chief source of copper worldwide, including in Madhya Pradesh (notably in the Malanjkhand copper mines).

EXPLANATION:

• CuFeS₂ (Chalcopyrite): The most important copper ore; occurs extensively in Madhya Pradesh; major source for commercial copper extraction.
• Cu₂O (Cuprite): An oxide ore of copper; less abundant and not the primary source in India.
• CuS (Covellite): A minor sulfide ore of copper; less economically important than chalcopyrite.
• CuSO₄ (Copper sulfate): A laboratory and industrial chemical; not a naturally occurring ore used for copper extraction.

Therefore, CuFeS₂ (Chalcopyrite) is the correct chemical formula of the primary copper ore found in Madhya Pradesh.

The correct answer is Bauxite.Key Points

• Bauxite is an aluminium-rich sedimentary rock formed from laterite soil.
• It is found in tropical or subtropical regions.
• Bauxite is used for the production of Aluminium.
• Bauxite is a non-ferrous metallic mineral that is used in the manufacturing of aluminium.
• Bauxite is found mainly in tertiary deposits and is associated with laterite rocks.

 Important Points

• Odisha is the largest bauxite-producing state in India.
• More than half of India's bauxite deposits are found in Odisha.
• Bauxite is an important mineral used in the production of aluminium.

 Additional Information

Important ores:

Concept:

Metal: It's an element that forms positive ions (cations) and has metallic bonds.

Physical Properties of Metals: 

• Ductility: Metals are ductile as they can be drawn into thin wires.
• Lustre: Metals have a shiny surface which is called metallic lustre.
• Hardness: Metals are generally hard and remain solid at room temperature. 
• Malleability: Metals are malleable, that is they can be beaten into thin sheets.
• Conductivity: Metals are good conductors of heat and electricity.
• ​Sonorous: All metals, except mercury, are sonorous i.e. they produce a sound on striking a hard surface. 
• Melting and Boiling Points: Metals have high melting and boiling points. 

Explanation:
Non-metals: They are opposite metals.

• They are neither malleable nor ductile.
• They are bad conductors of heat and electricity, except for graphite, which conducts electricity.
• Nonmetals generally have a low density as compared to metals.

Additional Information

Some important facts about metals:

Concept:

Process of Concentration

• The metal ores extracted contain impurities known as gauge particles. 
• The gauge particle is separated from the ore by the process known as concentration. 
• Froth flotation, magnetic separation, Leaching are some of the commonly used processes of concentration. 

Froth floatation method

• It is a process that selectively separates materials based upon whether they are water-repelling (hydrophobic) or have an affinity for water (hydrophilic).
• If the minerals are of Hydrophobic nature then only can get attracted toward froth and not with water.
• The process is commonly used for sulphide ores.
• This is because pine oil  used in the process selectively wets the sulphide ore and hence brings it to the froth.
• Froth flotation can primarily be done under two common techniques:
• • Direct floatation technique- The mineral sticks to the air bubble and the remaining gangue settles down at the bottom.
  • Reverse floatation technique- The gangue sticks to the air bubble and ore particle settle down in the bottom.

So, the correct option is Sulphide Ores. 

Additional Information:

Magnetic Separation

• Magnetic ores are mainly separated by magnetic separation method. 
• It has a conveyer belt with an electromagnetic. The powdered ore is made to pass through belt and electromagnet.

The correct answer is Cinnabar - Nickel.Key Points

• Cinnabar is a mercury sulfide ore and not a nickel ore.
• Bornite is an important copper ore that is also known as peacock ore due to its iridescent colors.
• Magnetite is a type of iron ore that is strongly magnetic and is used as a source of iron in steel making.
• Galena is a lead sulfide mineral that is the most important source of lead ore.

Additional Information

• Hematite is another important iron ore that is commonly found in sedimentary rocks and is used in the production of iron and steel.
• Chalcopyrite is a copper iron sulfide mineral that is the most important copper ore mineral.
• Sphalerite is a zinc sulfide mineral that is the most important zinc ore mineral.

The correct answer is Mercury.

Key Points

• A heavy, silvery d-block element, mercury is the only metallic element that is liquid under standard temperature and pressure conditions;
• The only other element that is liquid under these conditions is bromine, although metals such as cesium, gallium, and rubidium melt just above room temperature.

Additional Information

• Sodium:
  • Sodium is part of the alkali metal family along with lithium and potassium.
  • As one of the two ingredients of our table salt is its greatest reputation.
• Calcium:
  • Calcium with atom number 20 is represented in the periodic table by the symbol Ca.
  • Calcium (Ca) is an important element that makes our bones strong and able to withstand our loads.
• Lithium:
  • Lithium is a chemical element that appears first in the alkalis of the periodic table.
  • It is the lightest solid metal.

The correct answer is Bell Metal.

• Bell Metal alloy consists of copper and tin.

Key Points

• Bell metal is a hard alloy used for making bells and similar instruments, such as cymbals. 
• It is a form of bronze with a higher tin content, approximately a 4:1 ratio of copper to the tin.
• It is made of 80% copper and 20% tin (Sn) with some amount of Zinc and Lead.
• Bell metal is known for its resonance and attractive sound.

Additional Information

• ​Soft solder is an alloy of tin and lead.
• Hard solder is an alloy of copper and zinc.
• Rose's metal is an alloy of bismuth, lead and tin with 50% bismuth, 25–28% lead and 22–25% tin.
• German Silver is an alloy of copper, zinc and nickel.

Important Points

Some other important alloys are:

• German Silver - Cu + Zn + Ni
• Gun Metal - Cu + Sn + Zn + Pb
• Solder - Pb + Sn
• Brass - Cu + Zn
• Stainless steel - Fe + Cr + Ni + C​

The correct answer is option 1.

Concept:

• The Earth's crust is composed of a variety of elements, but some elements are more abundant than others.
• The composition of the Earth's crust has been studied extensively, and it is well-known that certain elements are the most abundant.
• These elements are determined based on their percentage by weight in the Earth's solid surface.

Explanations: 

• Al and Fe (Aluminum and Iron): Aluminum and iron are indeed among the most abundant elements in the Earth's crust.
• Aluminum is the most abundant metal, while iron is the fourth most abundant element. This option aligns with the concept.
• Al and Cu (Aluminum and Copper): Copper is not one of the most abundant elements in the Earth's crust. Copper is less abundant than both aluminum and iron. This option is not accurate.
• Fe and Cu (Iron and Copper): Copper is not among the most abundant elements in the Earth's crust. Iron is one of the most abundant elements, but copper is relatively less abundant. This option is not accurate.
• Cu and Ag (Copper and Silver): Copper is more abundant than silver in the Earth's crust, but neither copper nor silver are among the most abundant elements. This option is not accurate.  

The correct answer is Option 1: Al and Fe (Aluminum and Iron). 

The correct answer is Cu + Sn.

Key Points

• Bronze is the mixture of the metals tin and copper.
• The bronze alloy was made as early as the Harappan age.
• An alloy is considered a homogeneous mixture because, by definition, a homogeneous mixture has the same uniform appearance and composition throughout.
• Since an alloy is a mixture of two or more metals or a mixture of a metal with some other element, and these mixtures are uniform throughout, they fit the definition of being homogeneous.

Additional Information

The correct answer is All the alkali metals have two valence electrons.

Key Points

• Group 1 elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr) are known as alkali metals. Hence option 3 is correct.
• They are also known as s-block elements.
• The general electronic configuration of group 1 elements is ns1. It means they have only one electron in outermost shell. Hence option 4 is NOT correct.
• All alkali metals are soft, silvery white, with low densities, melting temperatures, and boiling points. Hence option 1 is correct.
• Melting point decreases down the groups in a periodic table.
• The ionization enthalpies of the alkali metals are considerably low and decrease down the group from Li to Cs. Hence option 2 is correct.
• Ionization Enthalpy is the minimum amount of energy required to remove a valance electron from an isolated gaseous atom (X) in its ground state.

Additional Information

• Due to ns1 electronic configuration, they have weak metallic bonding which explains their physical and chemical characteristics
• As we move down the group, this outer shell electron travel further from the nucleus.
• As a result, the atomic radii increases.
• As the ions get larger the distance between the bonding electrons and the positive nucleus gets larger and reduces the overall attraction between the two.

The correct answer is Tin.

Key Points

• Although tin is used in various alloys and has its own unique characteristics, it is not a common component of stainless steel.
  • Adding tin to stainless steel is not common and is not considered a standard ingredient in stainless steel production.
• Stainless steel is primarily composed of iron, along with chromium, nickel, and other elements. 
  • Chromium provides corrosion resistance to steel.
  • It exhibits exceptional corrosion resistance due to the formation of a very thin layer of Cr₂O₃ on the surface.
  • Nickel is usually added to stainless steel to increase its strength and hardness. It also improves corrosion resistance, especially in acidic environments.
  • An important type of stainless steel is often described as 18/8 steel where the chromium and nickel percentages are 18 and 8 respectively.