Question

The thermite reaction, ${\mathrm{Fe}}_2{\mathrm{O}}_3(s)+2\mathrm{Al}(s)⟶2\mathrm{Fe}(s)+$ ${\mathrm{Al}}_2{\mathrm{O}}_3(s),\mathrm{\Delta }{H}^{\circ }=-851.5\mathrm{kJ}/\mathrm{mol},$ is one of the most exother-mic reactions known. Because the heat released is sufficient to melt the iron product, the reaction is used to weld metal under the ocean. How much heat is released per mole of ${\mathrm{Fe}}_2{\mathrm{O}}_3$ produced? How does this amount of thermal energy compare with the energy released when 2 mol of protons and 2 mol of neutrons combine to form 1 mol of alpha particles?

Short answer

The heat released per mole of Fe2O3 produced in the thermite reaction is -851.5 kJ/mol. A comparison with the energy released in the nuclear reaction cannot be made without additional information.

Step-by-step solution

Determine the heat released per mole of Fe2O3 produced

The thermite reaction is given as: $F{e}_2{O}_3(s)+2Al(s)\to 2Fe(s)+A{l}_2{O}_3(s)$ The enthalpy change for the reaction, ΔH°, is given as -851.5 kJ/mol. This value is negative, indicating that the reaction is exothermic and releases heat. Since the enthalpy change is given per mole of reaction, and the stoichiometric coefficient for Fe2O3 is 1, the heat released per mole of Fe2O3 produced is -851.5 kJ/mol.

Compare the energy released with the energy released in the nuclear reaction

Given that 2 mol of protons and 2 mol of neutrons combine to form 1 mol of alpha particles, we need to find the energy released in this reaction for comparison. However, no information is provided regarding this nuclear reaction in the problem statement. Therefore, we cannot make the comparison without additional information. In conclusion, the amount of heat released per mole of Fe2O3 in the thermite reaction is -851.5 kJ/mol. To compare this with the energy released in the given nuclear reaction, additional information is needed.

Key concepts

Exothermic Reactions

Exothermic reactions are a type of chemical reaction that release energy, usually in the form of heat. This happens when the total energy of the products is lower than the energy of the reactants. The excess energy is released to the surroundings, causing the surroundings to get warmer. In the context of the thermite reaction, the reaction between iron(III) oxide, $F{e}_2{O}_3$, and aluminum, $Al$, is highly exothermic. The reaction produces molten iron and aluminum oxide, releasing a substantial amount of heat — enough to liquify the iron.

A key characteristic of exothermic reactions is that they have a negative enthalpy change, as noticeable in the thermite reaction where $\mathrm{\Delta }{H}^{\circ }=-851.5\mathrm{kJ}/\mathrm{mol}$. The negative sign indicates heat is released. Exothermic reactions are not only fascinating but also practical, finding uses in various industries such as welding and manufacturing.

Enthalpy Change

Enthalpy change measures the total heat content in a system under constant pressure. It is depicted as $\mathrm{\Delta }H$. For a reaction, if $\mathrm{\Delta }H$ is negative, it indicates an exothermic reaction, where heat is liberated. Conversely, a positive $\mathrm{\Delta }H$ signifies an endothermic process where heat is absorbed.

In the thermite reaction provided, the enthalpy change is $-851.5\mathrm{kJ}/\mathrm{mol}$ per mole of $F{e}_2{O}_3$ consumed. This large negative value signifies the substantial energy released during the reaction, which is characteristic of the formidable welding capabilities of the thermite reaction.

Enthalpy change is crucial in determining whether a reaction is energetically favorable as well as how the reaction might be employed in real-world applications, such as combining materials or creating energetic compounds.

Stoichiometry

Stoichiometry involves using balanced chemical equations to calculate the quantities of reactants and products involved in a chemical reaction. It is a fundamental concept in chemistry that ensures conservation of mass and allows chemists to predict the amounts of substances consumed and produced.

The thermite reaction equation $F{e}_2{O}_3(s)+2Al(s)\to 2Fe(s)+A{l}_2{O}_3(s)$ demonstrates how stoichiometry is used to balance the number of moles of each reactant and product. The coefficients before each compound indicate the moles in which they react. For example, 1 mole of $F{e}_2{O}_3$ reacts with 2 moles of $Al$, illustrating the stoichiometric relationship of reactants.

Stoichiometry is the backbone of calculating enthalpy changes and for planning the amounts of substances needed or produced in a chemical reaction. It is essential for accurately determining the heat released or absorbed, especially in highly exothermic reactions like the thermite reaction.