Problem 35 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

In the alumino-thermite process, aluminium acts as (a) an oxidizing agent (b) a flux (c) a reducing agent (d) a solder

Step-by-Step Solution

Answer

(c) a reducing agent

Step 1: Understanding the Alumino-thermite Process

The alumino-thermite process involves a reaction between aluminium and iron(III) oxide. This process is an exothermic chemical reaction where aluminium acts in a specific role to initiate the reaction.

Step 2: Identify Aluminium's Role

In this process, aluminium reacts with the oxides of metals like iron(III) oxide. The reaction can be represented as: \[ \text{Fe}_2\text{O}_3 + 2\text{Al} \rightarrow 2\text{Fe} + \text{Al}_2\text{O}_3 \]In this reaction, aluminium supplies electrons to the iron ions, which means it reduces the oxide to free metal.

Step 3: Determine the Function of Aluminium

Since aluminium donates electrons and reduces iron ions from iron(III) oxide to iron, aluminium acts as a reducing agent. A reducing agent is a substance that causes reduction by losing electrons itself.

Key Concepts

Oxidation-Reduction Reaction

In the world of chemistry, oxidation-reduction reactions, or redox reactions, play a central role. They involve the transfer of electrons between substances. In an oxidation-reduction reaction, one substance loses electrons (oxidation), while another gains electrons (reduction). This exchange is crucial for many chemical processes, including the alumino-thermite process.
In the alumino-thermite reaction, aluminum donates electrons to iron(III) oxide. This donation means aluminum undergoes oxidation, while iron(III) oxide undergoes reduction. In a simplified view:

• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.

This process simultaneously reduces iron(III) oxide to iron and oxidizes aluminum to aluminum oxide, making it an excellent example of a redox reaction.

Reducing Agents in Chemistry

Reducing agents are essential in chemical reactions with a focus on redox reactions. A reducing agent is a substance that donates electrons to another in a chemical reaction, causing reduction of the other substance. Here’s the catch: as the reducing agent donates electrons, it gets oxidized itself.
In the alumino-thermite process, aluminum serves as the reducing agent. It supplies electrons to iron(III) ions, transforming them into iron metal. This property of giving away electrons characterizes its function in the reaction:

• Easily loses electrons.
• Gets oxidized while reducing another substance.

By understanding reducing agents, we see how aluminum's role is pivotal in processes that bring about such dramatic transformations.

Exothermic Reactions

Exothermic reactions are those that release energy, usually as heat, into their surroundings. In the format of a reaction, they are often characterized by a negative change in enthalpy, \( \Delta H < 0 \). This means that the energy needed to start the reaction is less than the energy released.
The alumino-thermite process is a classic example of an exothermic reaction. In this process, the reaction between aluminum and iron(III) oxide releases a significant amount of heat. This heat can even produce molten iron directly from the reaction. Some quick pointers about exothermic reactions include:

• They release heat energy.
• They often feel hot to the touch.
• Energy release can be so extensive that it produces effects like molten substances.

Thus, understanding exothermic reactions helps to appreciate why the alumino-thermite process is both powerful and practical.