Problem 13 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The following reaction occurs in the Blast Furnace where iron ore is reduced to iron metal : \(\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+3 \mathrm{CO}(\mathrm{g}) \rightleftharpoons 2 \mathrm{Fe}(1)+3 \mathrm{CO}_{2}(\mathrm{~g})\) Using the Le Chatelier's principle, predict which one of the following will not disturb the equilibrium? (a) Removal of CO (b) Removal of \(\mathrm{CO}_{2}\) (c) Addition of \(\mathrm{CO}_{2}\) (d) Addition of \(\mathrm{Fe}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

(d) Addition of \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) does not disturb the equilibrium.

Step 1: Understand Le Chatelier's Principle

Le Chatelier's principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change and re-establish equilibrium. The principle helps predict the effect of changes in concentration, pressure, and temperature on a system at equilibrium.

Step 2: Identify the Reaction Components

The reaction is \[\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+3 \mathrm{CO}(\mathrm{g}) \rightleftharpoons 2 \mathrm{Fe}(1)+3 \mathrm{CO}_{2}(\mathrm{~g})\]The substances involved are \(\mathrm{Fe}_{2} \mathrm{O}_{3}(s)\), \(\mathrm{CO}(g)\), \(\mathrm{Fe}(l)\), and \(\mathrm{CO}_{2}(g)\). Solid substances do not affect the equilibrium in terms of concentration.

Step 3: Analyze the Impact of Each Option

- **(a) Removal of CO:** Decreases the concentration of a reactant, shifting the equilibrium to the left to produce more CO.- **(b) Removal of \(\mathrm{CO}_{2}\):** Decreases the concentration of a product, shifting the equilibrium to the right to produce more \(\mathrm{CO}_{2}\).- **(c) Addition of \(\mathrm{CO}_{2}\):** Increases the concentration of a product, shifting the equilibrium to the left to consume \(\mathrm{CO}_{2}\).- **(d) Addition of \(\mathrm{Fe}_{2} \mathrm{O}_{3}\):** This is a solid, and its change does not affect the equilibrium since solids and pure liquids do not affect the reaction quotient.

Step 4: Determine Which Change Does Not Affect Equilibrium

Based on Le Chatelier's principle, the addition of the solid reagent (\(\mathrm{Fe}_{2} \mathrm{O}_{3}\)) does not affect the balance of the gaseous components in the equilibrium reaction in terms of concentration.

Key Concepts

Chemical Equilibrium

Chemical equilibrium is a state in a chemical reaction where the rates of the forward and reverse reactions are equal. This balance results in no net change in the concentrations of the reactants and products. Consider the reaction happening in a blast furnace: \[\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+3 \mathrm{CO}(\mathrm{g}) \rightleftharpoons 2 \mathrm{Fe}(1)+3 \mathrm{CO}_{2}(\mathrm{~g})\]At equilibrium, this reaction continues in both directions at the same rate. If the system is undisturbed, the amounts of \(\mathrm{Fe}_{2} \mathrm{O}_{3}, \mathrm{CO}, \mathrm{Fe},\) and \(\mathrm{CO}_{2}\) remain constant. Changes in external conditions such as concentration, pressure, or temperature can shift this balance according to Le Chatelier's Principle, as the system seeks to restore equilibrium.

Reaction Quotient

The reaction quotient \(Q\) is a measure that determines the direction a reaction will proceed to reach equilibrium. It's calculated using the concentrations or pressures of the reactants and products at any moment, not necessarily at equilibrium. For a general reaction:\[aA + bB \rightleftharpoons cC + dD\]The reaction quotient \(Q\) is given as:\[Q = \frac{[C]^c [D]^d}{[A]^a [B]^b}\]In the equilibrium inside a blast furnace involving iron ore and carbon monoxide, only gaseous reactants and products affect \(Q\), since solids do not enter into the equilibrium expression. When \(Q\) is compared to the equilibrium constant \(K\), we can predict the direction of the shift to achieve equilibrium:

• If \(Q < K\), the reaction shifts to the right (forward) to form more products.
• If \(Q > K\), it shifts left (backward) to form more reactants.
• If \(Q = K\), the system is at equilibrium.

Blast Furnace

A blast furnace is a huge steel stack lined with refractory brick, where the production of iron from iron ore takes place. Inside, rocks containing iron ore, coke, and limestone are added from the top. Hot air blasts are introduced at the bottom, and a series of reactions occur as materials descend.In a blast furnace, the primary reaction is the reduction of iron oxides to iron metal. The ore, often hematite (\(\mathrm{Fe}_{2} \mathrm{O}_{3}\)), is reduced when carbon monoxide (a byproduct of coke combustion) acts as a reducing agent, transforming the ore into liquid iron. This process entails exothermic reactions creating layers of molten iron and slag, which are eventually tapped and removed.This setup is crucial as it allows indirect reduction, maximizing efficiency and the formation of hot gas streams that permeate the furnace, aiding the reduction process.

Iron Production

Iron production in a blast furnace is a major industrial process transforming iron ore into usable iron. This transformation involves a series of reactions where the solid iron ore is reduced to liquid iron through interactions mainly with coke and carbon monoxide.Hematite (\(\mathrm{Fe}_{2} \mathrm{O}_{3}\)) is amongst the most prevalent ores processed. The reaction depicted in our problem:\[\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+3 \mathrm{CO}(\mathrm{g}) \rightleftharpoons 2 \mathrm{Fe}(1)+3 \mathrm{CO}_{2}(\mathrm{~g})\]shows iron ore being reduced to molten iron through the removal of oxygen, facilitated by carbon monoxide.This process is continuous, with raw materials and air continuously introduced and products taken out, ensuring constant iron production. It is a careful balance of maintaining the right conditions within the furnace to allow ongoing efficient reduction and flow of materials.