General Principles And Processes Of Isolation Of Elements

The correct answer is Option is B) roasting followed by reduction with carbon

Zinc blende contains ZnS which is first roasted partially and then subjected to reduction with carbon

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The important ore of tin is cassiterite . Tin is extracted from cassiterite ore by carbon reduction method in a blast furnace. Limestone is added to produce a slug with impurities, which can be separated.

The product often contains traces of iron which is removed by blowing air through the melt to oxidise to FeO which then floats to the surface.

• Crude tin obtained initially contains impurities like iron, copper, lead, and other metals.
• The crude tin is subjected to a process called liquation, where it is remelted on an inclined furnace.
• Liquation takes advantage of the different melting points of tin and impurities.
• The easily fusible tin melts away and flows down, while the less fusible impurities remain behind.
• The molten tin is then further purified through a process called poling.
• Poling involves stirring the molten tin with green poles of wood in the presence of air.
• During poling, any remaining metal impurities react with oxygen in the air and form scum.
• The scum rises to the surface of the molten tin and is removed, leaving behind purified tin.
• Poling helps in oxidizing and removing the remaining impurities in the molten tin.

Therefore, Options A, C, and D are the correct answers.

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The electrochemical extraction of aluminum from bauxite involves several key processes. Let's analyze the given options:

• Option A: "The reaction of Al₂O₃ with coke (C) at a temperature > 2500°C."
  This is incorrect. High-temperature reactions involving coke are not part of the primary extraction methods for aluminum. Instead, the Hall-Héroult process uses electrolysis of alumina (Al₂O₃) in molten cryolite.
• Option B: "The neutralization of aluminate solution by passing CO₂ gas to precipitate hydrated alumina (Al₂O₃·3H₂O)."
  This is correct. In the Bayer process, sodium aluminate solution is neutralized by CO₂ to precipitate hydrated alumina, which is then converted into alumina (Al₂O₃) for further electrolysis.
• Option C: "The dissolution of Al₂O₃ in hot aqueous NaOH."
  This is correct. The Bayer process involves dissolving bauxite (Al₂O₃) in hot sodium hydroxide (NaOH), forming sodium aluminate, a key intermediate in alumina extraction.
• Option D: "The electrolysis of Al₂O₃ mixed with Na₃AlF₆ to give Al and CO₂."
  This is correct. The Hall-Héroult process involves electrolysis of alumina (Al₂O₃) dissolved in molten cryolite (Na₃AlF₆), producing aluminum metal (Al) and carbon dioxide (CO₂).

Final Answer: The correct options are: B, C, D.

The reaction of galena (PbS) with nitric acid (HNO₃) produces sulfur dioxide (SO₂) as the gas. The reaction is as follows:

The gas produced is sulfur dioxide (SO₂), which is a colorless gas with a pungent odor.

Now, let's analyze the properties of sulfur dioxide (SO₂), the gas produced during this reaction:

• Paramagnetic: Sulfur dioxide (SO₂) is paramagnetic because it has an unpaired electron in its molecular orbital, which causes it to be attracted by a magnetic field. SO₂ has a bent molecular geometry and contains an odd number of electrons.
• Bent in Geometry: The molecular geometry of SO₂ is bent due to the lone pairs of electrons on the sulfur atom, which causes repulsion. However, this does not directly relate to the gas properties as described in the options.
• Acidic Oxide: SO₂ is an acidic oxide because it reacts with water to form sulfurous acid (H₂SO₃). While this is true, the question primarily asks about the properties of the gas produced, which is sulfur dioxide.
• Colorless: SO₂ is colorless under standard conditions, making it a colorless gas.

Now, let's evaluate the given options:

• Option A: "Paramagnetic" – This is correct because SO₂ is paramagnetic due to its unpaired electron.
• Option B: "Bent in geometry" – This is incorrect because while SO₂ has bent geometry, the focus of the question is on the gas properties, not its molecular geometry.
• Option C: "An acidic oxide" – While SO₂ is indeed an acidic oxide, the primary focus of the question is on the gas properties (paramagnetic and colorless).
• Option D: "Colorless" – This is correct because SO₂ is a colorless gas under standard conditions.

Final Answer: The correct options are: A and D.