Question

The reaction of \(\mathrm{G}_{2}\) with \(\mathrm{E}_{2}\) to form \(2 \mathrm{EG}\) is exothermic, and the reaction of \(\mathrm{G}_{2}\) with \(\mathrm{X}_{2}\) to form \(2 \mathrm{XG}\) is endothermic. The activation energy of the exothermic reaction is greater than that of the endothermic reaction. Sketch the potential energy profile diagrams for these two reactions on the same graph.

Short answer

The potential energy diagram for these reactions would show an initial rise from the reactants to the peak of the activation energy, then a drop to the products for the exothermic reaction, and a further rise for the endothermic reaction. The peak for the exothermic reaction is higher than that for the endothermic reaction, indicating a higher activation energy for the exothermic reaction. The endpoint for the endothermic reaction is higher than its starting point, indicating energy absorption, while the endpoint for the exothermic reaction is lower than its starting point, indicating energy release.

Step-by-step solution

Understanding the concept

The first step is to understand the concept of exothermic and endothermic reactions. Exothermic reactions release energy to the surroundings, resulting in a decrease in potential energy. On the contrary, endothermic reactions absorb energy from the surroundings, resulting in an increase in potential energy. Therefore, in a potential energy diagram, exothermic reactions have a lower potential energy at the products compared to the reactants while endothermic reactions have a higher potential energy at the products.

Understanding the concept of activation energy

The second step involves understanding what activation energy means. Activation energy is the minimum energy required for a reaction to occur. In a potential energy diagram, this is represented as the 'hump' or peak that must be overcome for the reaction to proceed. The given exercise states that the activation energy of the exothermic reaction is greater than the endothermic reaction. This implies that the 'hump' for the exothermic reaction is higher than that of the endothermic reaction.

Drawing the potential energy diagrams

After understanding the concepts, it's now time to draw the potential energy diagrams. Draw two lines representing potential energy on the Y-axis and the reaction progress on the X-axis. For the exothermic reaction (G2 + E2), start by drawing a line rising from the left (representing the reactants), reaching a peak (representing the activation energy), and then falling down to a point lower than the initial level (representing the products). Similarly, for the endothermic reaction (G2 + X2), start by drawing a line rising from the left, reaching a peak (lower than the exothermic peak), and then rising further up to a point higher than the initial level. It's important to note that the final potential energy for the endothermic reaction is higher than the initial state, representing the absorption of energy.