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All questions of General Principles and Processes of Isolation of Metals for JEE Exam

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The purpose of adding cryolite is
  • a)
    to increase the electrical conductivity of pure aluminium
  • b)
    to lower the melting point of Al2O3
  • c)
    to remove the impurities as slag
  • d)
    to increase the Al% in the yield
Correct answer is option 'A'. Can you explain this answer?

Rohit Shah answered
Cryolite is used in the electrolysis of aluminium oxide. The mixture of cryolite and aluminium oxide has a lower melting point than pure aluminium oxide. This means a lower amount of energy is required to establish effective conditions for electrolysis and thus makes it more cost effective.

Can you explain the answer of this question below:

Which of the following contains both copper and iron?

  • A:

    Cuprite

  • B:

    Chalcocite

  • C:

    Chalcopyrite

  • D:

    Malachite

The answer is c.

Pooja Mehta answered
Chalcopyrite is a brass-yellow mineral with a chemical composition of CuFeS2. It occurs in most sulfide mineral deposits throughout the world and has been the most important ore of copper for thousands of years.
›  Chalcopyrite (CuFeS2) is the ore contains both copper and iron.
›  The largest deposit of nearly pure chalcopyrite ever discovered in Canada was at the southern end of the Temagami Greenstone Belt where Copperfield Mine extracted the high-grade copper.

Regarding cryolite incorrect statement is
  • a)
    It is an ore of Al 
  • b)
    The non-metal is fluorine
  • c)
    It is used in aluminium extraction from bauxite
  • d)
    Its formula is 3NaF. AIF3
Correct answer is option 'D'. Can you explain this answer?

Anisha Bose answered
Cryolite is an important ore of aluminum that is used in the extraction of aluminum from bauxite. It is a rare mineral that occurs in small quantities in Greenland, and its chemical formula is Na3AlF6.

One or More than One Options Correct Type
This section contains 5 multiple type questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.
Q. Which of the following is the correct combination?
  • a)
    Borax = Na2B4O7 . 5H2O
  • b)
    Colemanite = Ca2Br6O11 . 5H2O
  • c)
    Anglesite = PbCO3
  • d)
    Chile saltpeter = NaNO3
Correct answer is option 'D'. Can you explain this answer?

Nandini Iyer answered
Sodium nitrate is the chemical compound with the formula NaNO3. This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter.

Comprehension Type
This section contains a passage describing theory, experiments, data, etc. Two questions related to the paragraph have been given. Each question has only one correct answer out of the given 4 options (a), (b), (c) and (d)
                                                                           Passage
The natural substances in which metals occur in the earth are called minerals. A mineral has a definite composition. It may be a single compound or a complex mixture . It is usually associated with number of impurities. The minerals from which the metals can be conveniently extracted are called ores .Thus, all ores are minerals but all minerals are not ores. Depending on the composition ores are classified into different types such as oxides, sulphides, carbonates, halides, silicates etc.
Q. The impurities associated with minerals are called.
  • a)
    Gangue
  • b)
    Flux
  • c)
    Slag
  • d)
    Depressant
Correct answer is option 'A'. Can you explain this answer?

Priyanka Sharma answered
The correct answer is option A
The impurities associated with minerals used in metallurgy are collectively called Gangue.

Copper can be extracted from (1978)
  • a)
    Kupfernical
  • b)
    Dolomite
  • c)
    Malachite
  • d)
    Galena
Correct answer is option 'C'. Can you explain this answer?

Abhijeet Ingle answered
Malachite is a green copper carbonate hydroxide mineral with a chemical composition of cu2( co3)(oh)2
it was used as an ore of copper but is of minor importance today because of presence of copper in small quantities

Which metal is also found in sea beds ?
  • a)
    Magnesium
  • b)
    Calcium
  • c)
    Manganese
  • d)
    Aluminium
Correct answer is option 'C'. Can you explain this answer?

Kavita Joshi answered
Many thousands of square kilometres of the deep-sea floor are covered by metal-bearing nodules. They contain primarily manganese, but also nickel, cobalt and copper, which makes them economically promising.

Which one of the following is not a method of concentration of ore?
  • a)
    Gravity separation
  • b)
    Froth floatation process
  • c)
    Electromagnetic separation
  • d)
    Smelting
Correct answer is option 'D'. Can you explain this answer?

Vama Shah answered
Hey mate...Answer is smelting as it is the process of applying heat to the ore in order to extract the ore metal and the concn of ore is purely different than smelting so yah that's d reason behind hope it helped uh...!!!!!:)

For which oxide formation ΔG° is more negative than Gr2O3?
  • a)
    FeO
  • b)
    ZnO
  • c)
    Al2O3
  • d)
    MgO
Correct answer is option 'C,D'. Can you explain this answer?

Anuj Unni answered
Introduction:
The question asks us to determine which oxide formation has a more negative value of standard Gibbs free energy of formation (ΔG°f) compared to Gr2O3. The standard Gibbs free energy of formation is a measure of the thermodynamic stability of a compound, with more negative values indicating greater stability.

Analysis:
To compare the ΔG°f values of different oxides, we need to refer to the standard Gibbs free energy of formation data. By comparing the values, we can determine which oxide formation is more stable (i.e., has a more negative ΔG°f value) than Gr2O3.

Options:

a) FeO:
The standard Gibbs free energy of formation for FeO is -272.8 kJ/mol. Since FeO has a more negative ΔG°f value than Gr2O3, it is more stable.

b) ZnO:
The standard Gibbs free energy of formation for ZnO is -318.3 kJ/mol. Since ZnO has a more negative ΔG°f value than Gr2O3, it is more stable.

c) Al2O3:
The standard Gibbs free energy of formation for Al2O3 is -1582.3 kJ/mol. Since Al2O3 has a more negative ΔG°f value than Gr2O3, it is more stable.

d) MgO:
The standard Gibbs free energy of formation for MgO is -601.6 kJ/mol. Since MgO has a more negative ΔG°f value than Gr2O3, it is more stable.

Conclusion:
Based on the comparison of the standard Gibbs free energy of formation values, the oxide formations with more negative ΔG°f values than Gr2O3 are Al2O3 and MgO. Therefore, the correct answer is option C and D.

. Malachite is an ore of:
  • a)
    Copper
  • b)
    Magnesium
  • c)
    Calcium
  • d)
    Both magnesium and calcium
Correct answer is option 'A'. Can you explain this answer?

Mira Sharma answered
The distinctive bright-green hydrous CARBONATE MINERAL malachite is a common but minor ore of copper. It is usually found in copper deposits associated with LIMESTONE, occurring with AZURITE as the weathering product of other copper ore minerals.

In froth-floatation process, palm oil functions as :
  • a)
    Activator
  • b)
    Frother
  • c)
    Collector
  • d)
    Agitator
Correct answer is option 'B'. Can you explain this answer?

Surbhi Sengupta answered
Palm oil function as frother. It decreases the surface tension of the total solution, by which the formation of froth becomes easier.

Which method of purification is represented by the following equation ? [2012]
  • a)
    Zone refining
  • b)
    Cupellation
  • c)
    Polling
  • d)
    Van Arkel
Correct answer is option 'D'. Can you explain this answer?

Rohit Jain answered
Van Arkel is a method in which heat treatment is used to purify metal in this process metals are converted into other metal compound for loosly coupled like as iodine to make metal iodide which are easily decomposed and give pure metal.
The process is known as Van Arkel method.

Which technique utilizes the density difference between the ore and the impurity to concentrate the ore is
  • a)
    Leaching
  • b)
    Froth floatation
  • c)
    Magnetic separation
  • d)
    Levigation
Correct answer is option 'D'. Can you explain this answer?

Sravya Datta answered
Levigation is process of grinding an insoluble substance to a fine powder while wet. The material is introduced into mill together with water. It is based on the density difference between ore and impurity.

The different number of non-metals present in fluorapatite are
    Correct answer is '3'. Can you explain this answer?

    Sankar Singh answered
    Fluorapatite is a mineral that belongs to the apatite group. It has the chemical formula Ca5(PO4)3F and is composed of calcium, phosphorus, oxygen, and fluorine. The number of non-metals present in fluorapatite can be determined by analyzing its chemical formula.

    Chemical Formula of Fluorapatite
    - The chemical formula of fluorapatite is Ca5(PO4)3F.
    - The formula can be broken down into its constituent elements as follows:
    - Calcium (Ca)
    - Phosphorus (P)
    - Oxygen (O)
    - Fluorine (F)

    Non-Metals Present in Fluorapatite
    - Non-metals are elements that lack metallic properties such as malleability, ductility, and conductivity.
    - In the chemical formula of fluorapatite, the non-metals present are phosphorus, oxygen, and fluorine.
    - Calcium is a metal, and therefore, it is not considered a non-metal.

    Conclusion
    - Fluorapatite contains three non-metals, which are phosphorus, oxygen, and fluorine.

    Which is correctly matched?
    • a)
      Pyrometallurgy = Fe, Zn and Cu
    • b)
      Electrometallurgy = Al, Mg and Na
    • c)
      Hydrometallurgy = Ag and Au
    • d)
      Smelting = Fe, Cu, Ag
    Correct answer is option 'A,B,C'. Can you explain this answer?

    Anjana Sen answered
    Pyrometallurgy, Electrometallurgy, and Hydrometallurgy are three different processes used in metallurgy to extract metals from their ores. Each process is suitable for different types of ores and metals. The correct matches are:

    - Pyrometallurgy = Fe, Zn, and Cu
    - Electrometallurgy = Al, Mg, and Na
    - Hydrometallurgy = Ag and Au

    Now let's discuss each process in detail:

    1. Pyrometallurgy:
    Pyrometallurgy is a high-temperature process used to extract metals from their ores. It involves heating the ore in a furnace to produce a metal-rich product. This process is suitable for ores that can be easily heated and have high melting points. The correct matches for pyrometallurgy are:
    - Fe (iron): Iron is commonly extracted from its ore, hematite, using pyrometallurgical processes such as blast furnace smelting.
    - Zn (zinc): Zinc is extracted from its ore, zinc blende, through roasting and smelting processes.
    - Cu (copper): Copper is extracted from its sulfide ores, such as chalcopyrite, through roasting and smelting processes.

    2. Electrometallurgy:
    Electrometallurgy involves the use of electricity to extract metals from their ores. It uses electrolysis, where an electric current is passed through an electrolyte solution containing metal ions to deposit the metal on the cathode. The correct matches for electrometallurgy are:
    - Al (aluminum): Aluminum is extracted from its ore, bauxite, using the Hall-Héroult process, which involves electrolysis of molten aluminum oxide.
    - Mg (magnesium): Magnesium is extracted from its ore, magnesite, through electrolysis of molten magnesium chloride.
    - Na (sodium): Sodium is extracted through the electrolysis of molten sodium chloride.

    3. Hydrometallurgy:
    Hydrometallurgy uses aqueous solutions to extract metals from their ores. It involves dissolving the metal compounds in a suitable solvent, followed by precipitation or electrolysis to obtain the metal. The correct matches for hydrometallurgy are:
    - Ag (silver): Silver can be extracted from its ore, argentite, through a cyanide leaching process, followed by precipitation of silver ions with a reducing agent.
    - Au (gold): Gold can be extracted from its ore, gold-bearing quartz, through a cyanide leaching process, followed by precipitation of gold ions with a reducing agent.

    In conclusion, the correct matches for the given options are A, B, and C. Pyrometallurgy is suitable for Fe, Zn, and Cu extraction, Electrometallurgy is suitable for Al, Mg, and Na extraction, and Hydrometallurgy is suitable for Ag and Au extraction.

    The substance not likely to contain CaCO3 is –              [AIEEE-2003]
    • a)
      Sea shells
    • b)
      Dolomite
    • c)
      A marble statue
    • d)
      Calcined gypsum
    Correct answer is option 'D'. Can you explain this answer?

    Lavanya Menon answered
    The correct answer is option D
    A) On heating, gypsum loses water and gives the hemihydrate (CaSO4. 1/2H2O) or the anhydrite. The hemihydrate known as Calcined gypsum/ Plaster of Paris / stucco is an important building material.
    B) Seashells are the exoskeletons of mollusks such as snails, clams, oysters and many others. Such shells have three distinct layers and are composed mostly of calcium carbonate(CaCO​3).
    C) Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally CaMg(CO3​)2​. 
    D) A marble statue typically consists of calcium carbonate.
    So Calcined gypsum does not have calcium carbonate.

    In the froth floatation process for benefaction of the ores, the ore particles float because
    • a)
      They are light
    • b)
      Their surface is not easily wetted by water
    • c)
      They are insoluble
    • d)
      They bear electric charge
    Correct answer is option 'B'. Can you explain this answer?

    Rishika Chauhan answered
    The ore particles preferentially wetted by the oil become lighter and thus rise to the surface along with the froth while the gangue particle wetted by wated become heavier and thus settle down at the bottom.

    Refining of silver is done by :
    • a)
      Liquation
    • b)
      Poling
    • c)
      Cupellation
    • d)
      Van Arkel method
    Correct answer is option 'C'. Can you explain this answer?

    Kiran Khanna answered
    Cupellation is the process used for refining silver. During this process, impure silver is heated in a cupel (a small, shallow, porous ceramic or bone ash container) along with lead oxide (PbO) as the oxidizing agent. The impurities present in the silver form certain compounds that are either volatile or soluble in the molten lead, while the pure silver remains behind as a residue.

    Here is a detailed explanation of the cupellation process:

    1. Preparation: The impure silver is first melted and cast into small bars or pellets. These pellets are then placed in the cupel.

    2. Cupellation: The cupel, along with the pellets of impure silver, is heated in a furnace at a temperature of around 900-1000°C. As the temperature rises, the lead oxide (PbO) in the cupel reacts with the impurities in the silver, forming various compounds.

    3. Oxidation of Impurities: The lead oxide acts as an oxidizing agent, converting the impurities into compounds that are either volatile or soluble in the molten lead. This includes impurities like copper, iron, and other base metals present in the silver.

    4. Volatilization: Some impurities form volatile compounds, such as copper forming copper oxide (CuO) and iron forming iron oxide (FeO). These compounds vaporize and escape from the cupel, leaving behind the pure silver.

    5. Formation of Lead Button: The impurities that are not volatile or soluble in the molten lead form a molten lead-silver alloy. This alloy collects at the bottom of the cupel and solidifies into a button-like mass.

    6. Removal of Lead: The lead button is then separated from the cupel. It can be further processed to recover the lead or recycled for future cupellation processes.

    7. Collection of Pure Silver: The residue left in the cupel after the removal of the lead button is pure silver. It may still contain trace amounts of other impurities, but it is significantly refined compared to the initial impure silver.

    8. Further Refinement: The pure silver obtained from cupellation can undergo additional refining processes, such as electrolysis or chemical precipitation, to achieve even higher levels of purity.

    Overall, cupellation is a crucial step in the refining of silver, allowing for the removal of impurities and the production of high-quality, pure silver.

    In the leaching of Ag2S with NaCN the equation is
    Ag2S + 4NaCN → 2Na[Ag(CN)2] + Na2S. In this change in oxidation state of silver.
      Correct answer is '0'. Can you explain this answer?

      Anjana Sen answered
      The Leaching of Ag2S with NaCN: Change in Oxidation State of Silver

      The leaching process involves the extraction of a metal from its ore by using a suitable solvent. In the case of the leaching of Ag2S (silver sulfide) with NaCN (sodium cyanide), the reaction equation is as follows:

      Ag2S + 4NaCN → 2Na[Ag(CN)2] + Na2S

      In this reaction, the silver sulfide (Ag2S) reacts with sodium cyanide (NaCN) to form sodium dicyanoargentate(I) (Na[Ag(CN)2]) and sodium sulfide (Na2S). Let's analyze the change in the oxidation state of silver in this reaction.

      The Oxidation State of Silver in Ag2S
      In Ag2S, silver exists as a +1 oxidation state. This is because sulfide (S2-) has an oxidation state of -2, and since Ag2S is a neutral compound, the oxidation state of silver must balance the charge, resulting in a +1 oxidation state.

      The Oxidation State of Silver in Na[Ag(CN)2]
      In Na[Ag(CN)2], the sodium ion (Na+) has a fixed oxidation state of +1. The cyanide ion (CN-) has a -1 oxidation state. Therefore, to maintain charge neutrality in the compound, the oxidation state of silver must be +1. This is the same as the oxidation state of silver in Ag2S.

      Conclusion
      The change in oxidation state of silver during the leaching of Ag2S with NaCN is zero. The silver starts with a +1 oxidation state in Ag2S and remains in the +1 oxidation state in Na[Ag(CN)2]. This is because the cyanide ions in NaCN act as a ligand, forming a coordination compound with the silver ion, but do not cause a change in its oxidation state.

      Overall, the leaching of Ag2S with NaCN is a redox-neutral process, where the silver ions do not undergo any change in their oxidation state.

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