The speed at which reactants are converted into products during a reaction is referred to as its rate. The rate of a reaction is most commonly defined as the change in reagent concentration per unit time. Most reactions, however, have rates that change as the reaction proceeds; studies, therefore, use a reaction's initial rate to avoid ambiguity. The initial rate is the rate measured at the beginning of a reaction before an appreciable change in reagent concentration occurs.
Energy diagrams (also called energy level diagrams, or reaction coordinate diagrams) are used to depict energy changes occurring in a reaction. The maximum energy of the reaction is called the transition state energy, with the difference in energy between this and the energy of the reactants named the activation energy. The activation energy is the energy barrier the reactants must overcome in order to react. The energy change of a reaction is also illustrated on the reaction coordinate diagram; this energy change, the difference between that of the products and reactants, is delta E.
This module simulates a unimolecular decomposition reaction of a blue compound in solution. The reaction begins in a beaker containing a solution light blue in color; the intensity of the color in the beaker is proportional to the concentration of the blue reacting species. When the simulation is complete, the color of the beaker is that after a reaction time of 100. seconds. Each time a reaction runs, the initial rate of is reported. The reaction rate is also represented graphically by a plot of concentration vs. time. In addition, an energy coordinate diagram for the reaction is accessible. It is important to realize that adjusting the temperature in this simulation really adjusts the conditions under which the reaction takes place, and does not indicate anything about energy gained or released during the reaction. We are assuming that energy gained or released by the reactants is negligible and that the temperature of the system remains constant during the reaction.
INSTRUCTIONS
1. Select an initial concentration value by adjusting the [A]o scroll bar.
2. Select an initial temperature by adjusting the oC scroll bar.
3. Select an initial enthalpy value by adjusting the Delta E scroll bar.
4. Select an initial activation energy value by adjusting the Ea scroll bar.
5. Begin the reaction by clicking on the React button.
6. The reaction rate plot will overlay multiple graphs. To clear the plot
