Final answer:
The rate of dissociation refers to how quickly a combined substance separates into individual entities, which is not the same as the reaction rate for A and B combining to form AB. The rate of a reaction is related to the concentrations of the reactants and can be calculated by considering the stoichiometry of the reaction. Second-order reactions have rates that are proportional to the product of concentrations of each reactant.
Step-by-step explanation:
The rate of dissociation in the context of the reaction A + B → AB refers to the speed at which the reactants A and B separate from each other to form individual entities, assuming the reaction is at equilibrium and can proceed in both forward and reverse directions. However, the provided question pertains to a combination reaction where A and B are combining to form AB, which suggests we should discuss the rate of association or formation rather than dissociation. In chemical kinetics, this rate can be expressed in terms of the decrease in the concentration of A or the increase in the concentration of B. The rates of formation and disappearance of species in a reaction are related by the stoichiometry of that reaction.
For instance, in the example reaction 5Br⁻(aq) + BrO3⁻(aq) + 6H+⁺(aq) → 3Br2(aq) + 3H2O(l), if the rate of disappearance of Br⁻(aq) at a particular moment during the reaction is 3.5 × 10⁻4 mol L⁻¹ s⁻¹, the rate of appearance of Br2(aq) can be calculated by considering the stoichiometry of the reaction, which shows that 5 moles of Br⁻ give 3 moles of Br2. Therefore, the rate of appearance of Br2 would be a fraction of the rate of disappearance of Br⁻, specifically (3/5) × 3.5 × 10⁻4 mol L⁻¹ s⁻¹.
In general, the rate law expresses how the rate depends on the concentration of the reactants. For a second-order reaction, where the reaction is first order both in A and B, the rate is proportional to the product of the concentrations of each reactant. The integrated rate law for reactions of different orders can vary, but the overall concept of the rate being dependent on the reactant concentrations remains consistent.