Question

The thermite reaction produces so much energy (heat) that the iron is initially formed as a liquid. \(2 \mathrm{Al}(s)+\mathrm{Fe}_{2} \mathrm{O}_{3}(s) \rightarrow 2 \mathrm{Fe}(s)+\mathrm{Al}_{2} \mathrm{O}_{3}(s)\) Describe the transfer of electrons for both the aluminum and iron.

Short answer

In the thermite reaction, aluminum undergoes oxidation as its oxidation state increases from 0 to +3, losing 3 electrons per atom. Simultaneously, iron undergoes reduction, with its oxidation state decreasing from +3 to 0, gaining 3 electrons per atom. As two aluminum atoms lose a total of 6 electrons, these electrons are transferred to two iron atoms in the \(\mathrm{Fe}_2\mathrm{O}_3\) compound, which require the same number of electrons for their reduction. This transfer of electrons results in the formation of liquid iron and aluminum oxide as products.

Step-by-step solution

Identify the oxidation states of elements

To start, we need to find the oxidation states of aluminum (Al) and iron (Fe) in the given equation. In the reactants, aluminum is in its elemental state, so its oxidation state is 0. Iron is in the compound \(\mathrm{Fe}_2\mathrm{O}_3\), where it has an oxidation state of +3 because oxygen has an oxidation state of -2. In the products, iron is in its elemental state, so its oxidation state is 0. Aluminum is in the compound \(\mathrm{Al}_2\mathrm{O}_3\), where it has an oxidation state of +3 because oxygen has an oxidation state of -2.

Determine the oxidation and reduction processes

Now, we can determine which element undergoes oxidation and which undergoes reduction. The oxidation state of aluminum increases from 0 in the reactants to +3 in the products. This means aluminum is oxidized. The oxidation state of iron decreases from +3 in the reactants to 0 in the products, meaning that iron is reduced in the reaction.

Describe the transfer of electrons

During the thermite reaction, aluminum loses 3 electrons to attain an oxidation state of +3, undergoing oxidation. As each aluminum atom loses 3 electrons, the 2 aluminum atoms lose a total of 6 electrons. These electrons are transferred to the iron present in the \(\mathrm{Fe}_2\mathrm{O}_3\) compound. Each iron atom gains 3 electrons because its oxidation state changes from +3 to 0, requiring a total of 6 electrons for the 2 iron atoms. As a result, the 6 electrons lost by the aluminum atoms are gained by the iron atoms in the \(\mathrm{Fe}_2\mathrm{O}_3\) compound. This transfer of electrons leads to the formation of liquid iron and aluminum oxide as products of the thermite reaction.

Key concepts

Electron Transfer in Redox Reactions

Understanding the flow of electrons during chemical reactions is crucial in the study of chemistry, especially in redox reactions, where the movement of electrons from one substance to another occurs. In the context of the thermite reaction, we're looking at a vivid demonstration of an exothermic redox process.

Let's break it down. Redox is a combination of two processes: reduction and oxidation. Oxidation involves the loss of electrons while reduction involves the gain of electrons. This interplay is guided by a principle where the substance that donates electrons, undergoing oxidation, is known as the reducing agent. Conversely, the substance that accepts electrons, undergoing reduction, is known as the oxidizing agent.

In the thermite reaction, aluminum \texttt{(Al)} acts as a reducing agent. It loses electrons and increases its oxidation state from 0 to +3. On the flip side, iron in the form of iron(III) oxide \texttt{(Fe\(_2\)O\(_3\)}) serves as the oxidizing agent. It gains the electrons lost by aluminum, reducing its oxidation state from +3 to 0, and transforms into metallic iron. This electron shift is not merely a hypothetical transfer but a concrete change that can be observed through the intense heat and liquid iron produced.

Oxidation States Determination

In order to fully comprehend the electron transfer in a redox reaction, it is essential to determine the oxidation states of the involved elements. The oxidation state, which can also be called the oxidation number, is a theoretical charge that an atom would have if the compound was composed of ions. It helps chemists keep track of electron distribution during chemical reactions.

To pinpoint oxidation states, certain rules must be followed, such as oxygen usually having an oxidation state of -2, and elements in their elemental form having an oxidation state of 0. When we apply these rules to the thermite reaction, we start by recognizing that elemental aluminum \texttt{(Al)} has an oxidation state of 0. Iron, on the other hand, bound in the compound iron(III) oxide \texttt{(Fe\(_2\)O\(_3\))}, assumes an oxidation state of +3 since it's bonded to oxygen. After the reaction, aluminum, now part of aluminum oxide \texttt{(Al\(_2\)O\(_3\))}, holds an oxidation state of +3. Iron, now in its elemental state, returns to an oxidation state of 0.

This change in oxidation states during the reaction is indicative of the shift in electron density between the reactants, leading to the formation of new products. Understanding these states is fundamental for analyzing and predicting the outcomes of redox reactions.

Chemical Equations and Stoichiometry

Chemical reactions are represented by chemical equations, which reflect the substances involved, their proportions, and the end products. Stoichiometry plays a pivotal role in this representation, as it is the part of chemistry that deals with the relative quantities of reactants and products in chemical reactions.

For instance, the stoichiometry in the balanced thermite equation indicates that for every two moles of aluminum used, one mole of iron(III) oxide is required. This results in the creation of two moles of iron and one mole of aluminum oxide as products. A balanced equation not only ensures that mass is conserved but also that the number of electrons lost by the reducing agent equals the number gained by the oxidizing agent.

When practicing stoichiometry, we use coefficients to balance the equation. These coefficients give us the exact mole ratio needed to react substances completely, with no excess or shortfall of reactants. Particularly in the thermite reaction, this precise mole ratio is critical for the safety and efficiency of the process, ensuring that correct amounts of reactants yield the expected amount of heat and products.