13-1-chemical-equilibria_summary

The provided text discusses the concept of chemical equilibria in chemistry. Chemical equilibrium refers to a state where the rates of forward and reverse reactions in a reversible chemical reaction are equal, causing the concentrations of reactants and products to remain constant over time. A chemical equation, with reactants on the left and products on the right, represents the reaction as proceeding from left to right, but reversible reactions can proceed in both directions. The text describes an example of the reversible decomposition of dinitrogen tetroxide, which forms brown nitrogen dioxide, using a special double arrow to emphasize the reversible nature of the reaction. The forward and reverse reaction rates vary over time, with the forward reaction initially proceeding at a finite rate and the reverse reaction initially at zero, as the concentration of the reactant falls and the product concentration rises. This continues until the forward and reverse reaction rates become equal, at which point the reaction is at equilibrium, with constant concentrations of its reactants and products. The text also highlights the dynamic nature of chemical equilibria, emphasizing that a reaction at equilibrium is not "stopped" but is proceeding in both the forward and reverse directions at the same rate. To further illustrate this point, the text uses the example of a two-person juggling act, where both individuals are throwing and catching objects at the same rate, maintaining a relatively constant number of objects. Finally, the text mentions that physical changes, such as phase transitions, can also establish equilibria, using the vaporization of bromine as an example. In this case, when liquid bromine is added to a sealed container, the forward process (vaporization) will continue at a constant rate until the rate of the reverse process (condensation) equals the rate of vaporization, establishing equilibrium. A photograph showing this phase transition equilibrium is provided.