General Principles And Processes Of Isolation Of Elements

An oxidation-reduction reaction occurring in a blast furnace is required to create iron from its ore.

As carbon is a more reactive element than iron, it is utilized to reduce iron using carbon monoxide (CO).

When carbon combines with oxygen, it creates carbon monoxide, which subsequently reacts with iron oxide to create elemental iron.

2C + O₂ → 2CO

Fe₂O₃ + 3CO → 2Fe + 3CO₂

Magnetite and hematite are sources of iron. The two most typical iron ores are these two.

 By adding ore, limestone, and coke to the blast furnace, iron may be produced from hematite. Metal silicates that are iron-bearing are the major contaminant in hematite.

The reduction of ferrous oxides in the molten ore in the blast furnace is the first step in the extraction process. In the blast furnace, carbon-based coke combines with oxygen to produce carbon monoxide and iron oxides that have been reduced by carbon monoxide.

Potassium ethylxanthate is used as a collector in the froth flotation process. It is used to make the ore particles hydrophobic. By making the ore particles hydrophobic, they are more likely to attach to the bubbles in the flotation tank, allowing the desired ore to float to the surface, where it can be separated from other materials. In this context, the term "lighter" is used to describe the ore's ability to float. The ore becomes more buoyant in the flotation medium due to its hydrophobic properties.
Thus, the function of potassium ethylxanthate is to make the ore lighter.

The Hall-Heroult process is used for the extraction of aluminum from its ore, bauxite. It involves the electrolysis of molten aluminum oxide (Al O ), and the following points are true for this process:

• Option A: Carbon anode is oxidized to CO and CO — This is correct. In the Hall-Héroult process, the carbon anode undergoes oxidation, releasing carbon dioxide (CO ) and carbon monoxide (CO) gases.
  
  Option B: Na AlF helps to decrease the melting point of the electrolyte — This is also correct. Sodium hexafluoroaluminate (Na AlF ), commonly known as cryolite, is added to the electrolyte to lower its melting point and make the process more efficient.
  
  Option C: CaF helps to increase the conductivity of the electrolyte — This is correct. Calcium fluoride (CaF ) is added to increase the conductivity of the molten electrolyte.
  
  Option D: Oxidation state of oxygen changes in the overall cell reaction — This is incorrect. In the overall cell reaction, oxygen remains in the same oxidation state. Oxygen ions are reduced at the cathode to form aluminum, and at the anode, oxygen ions are oxidized to produce oxygen gas, but the oxidation state of oxygen remains -2 in both cases.

Thus, the incorrect statement is (D). The oxidation state of oxygen does not change in the overall cell reaction.

Therefore, the correct answer is (D).

To determine the correct statement from the given options, we need to understand the processes of roasting, calcination, and smelting in metallurgy.

1. Roasting: This process involves heating the ore in the presence of excess air or oxygen. It is primarily used for sulfide ores to convert them into oxides, releasing sulfur dioxide gas. The statement "Roasting involves heating the ore in the absence of air." is incorrect.
2. Calcination: This process involves heating the ore in the absence or limited supply of air, typically below or at its melting point, to bring about thermal decomposition. The statement "Calcination involves heating the ore above its melting point." is incorrect as it focuses on thermal decomposition without reaching melting points.
3. Smelting: This process involves heating the ore with a suitable reducing agent (like carbon) and a flux in order to extract the base metal. This process generally occurs below the melting point of the metal in question. However, as described, smelting often reaches temperatures above the melting points to combine and melt the materials together. Thus, the statement "Smelting involves heating the ore with a suitable reducing agent and flux below its melting point." is incorrect.
4. Calcination of Calcium Carbonate: This is an endothermic reaction where calcium carbonate ( ) is decomposed into calcium oxide ( ) and carbon dioxide ( ) with the absorption of heat: The statement "Calcination of calcium carbonate is endothermic." is correct.

The correct answer is that the calcination of calcium carbonate is endothermic, making option 4 the right choice. This is due to the absorption of heat required to decompose into and .