Suppose that the reaction \(\mathrm{A} \longrightarrow\) products is exothermic and has an ac- tivation barrier of 75 \(\mathrm{kJ} / \mathrm{mol} .\) Sketch an energy diagram showing the en- ergy of the reaction as a function of the progress of the reaction. Draw a second energy curve showing the effect of a catalyst.

An exothermic reaction is a chemical process that releases energy in the form of heat or light. In the context of a student's energy diagram exercise, understanding an exothermic reaction is crucial.

When reactants are transformed into products, energy stored within chemical bonds is often released. This release occurs because the total energy of the products is lower than that of the reactants. On an energy diagram, this is represented by showing the products at a lower potential energy level compared to the reactants.

The decline from the reactants' energy level to the products' energy level visually illustrates the energy released. For the exercise given, you would start by plotting the reactants' energy, then drawing a downward trajectory to the products' energy, indicating an energy release. This visualization aids in grasilping the concept that during an exothermic reaction, the surrounding environment absorbs energy.

Energy Release in Real-World Applications

Exothermic reactions are not just textbook examples; they're abundant in everyday life. When wood burns, producing heat and light, or when our bodies metabolize food converting it into energy, these are practical instances of exothermic processes.

Activation energy is fundamental to understanding chemical reactions. It refers to the minimum amount of energy needed to initiate a reaction. In other words, it's the 'energy barrier' that reactants must overcome for a reaction to proceed.

In the provided energy diagram exercise, students are asked to indicate an activation barrier of 75 kJ/mol, which means that reactants require this amount of energy to transform into products. On an energy diagram, the activation energy is depicted as a peak that the reactants must 'climb' before descending to the energy level where the products reside.

The concept of activation energy helps explain why not all reactions occur spontaneously, even if they are exothermic. For instance, gasoline does not ignite without the energy provided by a spark. By knowing how much energy is needed, chemists can understand reaction rates and how different conditions might affect a reaction.

Catalysts are substances that increase the rate of a chemical reaction without undergoing permanent chemical change themselves. They achieve this by providing an alternative reaction pathway with a lower activation energy. In the context of the exercise, a catalyst's role is depicted as lowering the peak representing the activation energy on the energy diagram.

A catalyst does not alter the initial or final energy levels of the reactants and products; rather, it makes it easier for reactants to reach the transition state, thus speeding up the reaction. On a plotted energy diagram for a catalyzed reaction, students should ensure that the peak for the activation energy with the catalyst is noticeably lower than the uncatalyzed activation energy.

Catalysts in Everyday Life

Everyday applications of catalysts include catalytic converters in cars, which reduce harmful emissions, and enzymes in our bodies, which catalyze biochemical reactions necessary for life. In an educational setting, teaching about catalysts equips students to understand why these additives are often essential in chemical processes, whether in industrial manufacturing or in living organisms.