Problem 3 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the follwoing reaction occurs in the com. bustion zone of the blast furnace during the extractior of iron? (a) \(\mathrm{CO}_{2}+\mathrm{C} \longrightarrow 2 \mathrm{CO}\) (b) \(\mathrm{CaO}+\mathrm{SiO}_{2} \longrightarrow \mathrm{CaSiO}_{3}\) (c) \(\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}\) (d) \(\mathrm{FeO}+\mathrm{CO} \longrightarrow \mathrm{Fe}+\mathrm{CO}_{2}\)

Step-by-Step Solution

Answer

(c) \(\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}\) occurs in the combustion zone.

Step 1: Identify the Purpose of Combustion Zone

In a blast furnace, the combustion zone is where the fuel reacts with oxygen to produce heat and form gases necessary for the reduction of iron ores.

Step 2: Analyze Reaction Options

Look at each reaction and determine if it is a combustion reaction, which typically involves oxygen and produces energy and gas.- (a) \(\mathrm{CO}_{2}+\mathrm{C} \longrightarrow 2 \mathrm{CO}\) involves the conversion of carbon dioxide to carbon monoxide.- (b) \(\mathrm{CaO}+\mathrm{SiO}_{2} \longrightarrow \mathrm{CaSiO}_{3}\) is a mineral formation, not a combustion reaction.- (c) \(\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}\) involves carbon and oxygen forming carbon dioxide, a classic combustion reaction.- (d) \(\mathrm{FeO}+\mathrm{CO} \longrightarrow \mathrm{Fe}+\mathrm{CO}_{2}\) involves the reduction of iron oxide.

Step 3: Determine Combustion Reactions

Identify reactions that involve oxygen and produce energy. Reaction (c) \(\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}\) involves combustion because it uses oxygen and produces carbon dioxide, releasing substantial energy necessary for the blast furnace operation.

Step 4: Confirmation by Elimination

After identifying that option (c) fits the description of a combustion reaction, confirm by recognizing that other options either do not produce energy or are not primarily related to the fuel combustion process itself.

Key Concepts

Combustion Reaction

A combustion reaction is a chemical process where a substance combines with oxygen, releasing energy in the form of heat or light. A classic example is when carbon (c) reacts with oxygen (o_{2}) to form carbon dioxide (co_{2}). This process is essential in many industrial applications, including the blast furnace used for iron extraction.
In the context of a blast furnace, the combustion zone is crucial. Here, coke, which is primarily composed of carbon, burns in the presence of oxygen supplied through hot air blasts. This reaction:

• c+o_{2} rightarrow co_{2}

generates the extreme temperatures required for melting iron ores. The energy released from the combustion reaction not only aids in boosting the temperature but also supports subsequent reactions needed for iron extraction.

Iron Extraction Process

The iron extraction process in a blast furnace is a series of complex reactions aimed at transforming iron ore into metallic iron. The primary material in this procedure is iron ore, typically in the form of hematite ( fe_{2}o_{3}) or magnetite ( fe_{3}o_{4}), along with coke and limestone.
These raw materials are layered within the furnace. The heat from the combustion zone facilitates the reduction of iron oxides. This is done by converting them into pure iron using carbon monoxide ( co) formed from the initial combustion of coke.

• The main reduction reaction: feo + co arrow fe + co_{2}

results in the liberation of iron from its oxides, while the carbon monoxide acts as a reducing agent.

Chemical Reactions in Metallurgy

Metallurgy involves multiple chemical reactions, particularly in the processing and extraction of metals from ores. Each segment of the blast furnace has its specific reaction profile. Apart from combustion and reduction reactions, other metallurgical processes contribute to successful iron extraction.
One key reaction involves the formation of slag, a byproduct of impurity removal:

• cao + sio_2 arrow casio_3

This interaction between lime ( cao) and silica ( sio_{2}) purges impurities from the molten iron, forming easily removable slag. This purification is just as critical, ensuring that the end product, which is the refined iron, meets quality standards for further industrial applications.
Understanding these reactions provides valuable insights into the metallurgical processes that are foundational to modern industrial chemistry.