Problem 77 - A Complete Resource Book in Chemistry for JEE Main

Question

The reducing agent in thermite process is (a) \(\mathrm{Mg}\) (b) \(\mathrm{BaO}_{2}\) (c) \(\mathrm{Al}\) (d) \(\mathrm{MnO}_{2}\)

Step-by-Step Solution

Answer

The reducing agent is (c) \( \mathrm{Al} \).

Step 1: Understanding the Thermite Process

The thermite process is an exothermic reaction used to produce elemental metal from oxides. It involves a metal oxide and a more reactive metal that reduces the oxide to the elemental metal.

Step 2: Identifying the Reaction Components

In the thermite process, the typical reactants used are a metal oxide and aluminum powder. Aluminum acts as the more reactive reducing agent and reduces the metal oxide to its elemental form while being oxidized to aluminum oxide.

Step 3: Selecting the Correct Reducing Agent

Given options are  Mg,  BaO,  Al,  MnO. The thermite process specifically uses aluminum as the reducing agent due to its high reactivity and ability to release energy.

Key Concepts

Exothermic Reaction

The thermite process is a prime example of an exothermic reaction, which is a reaction that releases heat energy to the surroundings. The basic characteristic of such reactions is that they liberate energy, often in the form of heat or light. The significance of this reaction lies in its ability to produce immense temperatures, often reaching over 2500°C. This capability is what makes exothermic reactions highly useful for industrial applications.

In the context of the thermite process, this intense heat is used to melt and reduce metal oxides to their elemental states. It demonstrates how the energy released from these types of reactions can be harnessed for practical purposes. Often, these reactions proceed spontaneously after an initial energy input. Think of it like lighting a spark; once started, the reaction continues and provides energy. This makes exothermic reactions highly efficient in processes where heat generation is crucial.

Reducing Agent

In chemical reactions, a reducing agent plays a pivotal role in the process of reduction. A reducing agent is a substance that donates electrons to another substance, thus reducing it. Simultaneously, the reducing agent itself gets oxidized.

During the thermite process, aluminum acts as the reducing agent. It is highly effective due to its ability to donate electrons easily. When aluminum is combined with a metal oxide, it donates electrons to reduce the metal oxide to its pure metal form. Meanwhile, the aluminum itself is oxidized to form aluminum oxide.

The selection of a suitable reducing agent like aluminum is based on its high reactivity, which ensures a fast and complete reduction reaction. This principle is essential to many metallurgical practices, where different reducing agents may be chosen depending on the desired result and the characteristics of the metals involved.

Aluminum Reduction

In the thermite process, aluminum's role as a reducing agent is integral to the occurrence of reduction. Aluminum is chosen because of its high affinity for oxygen, which means it can easily take up oxygen from metal oxides. This ability makes aluminum a powerful agent in metallurgical reactions, especially in the thermite process used to extract metals like iron from their oxides.

To see how aluminum reduction works, consider the reaction with iron(III) oxide: the aluminum reduces iron(III) oxide (Fe_2O_3) to iron (Fe), while the aluminum itself is oxidized to generate aluminum oxide (Al_2O_3). The equation for this reaction is:

\[\mathrm{Fe_2O_3} + 2\mathrm{Al} \rightarrow 2\mathrm{Fe} + \mathrm{Al_2O_3} + \text{Heat}\]
This equation highlights the dual role of aluminum in obtaining the metal and forming an oxide. The resultant heat is immense, supporting the idea of exothermic reactions releasing a substantial amount of energy. Through aluminum reduction, valuable metals can be extracted efficiently, demonstrating its broad applications in industry and its foundational role in different metal extraction processes.