Private: Chapter Seventeen
Key Terms, Key Equations, Summaries, and Exercises (Chapter 17)
- activated complex
- (also, transition state) unstable combination of reactant species formed during a chemical reaction
- activation energy (Ea)
- minimum energy necessary in order for a reaction to take place
- Arrhenius equation
- mathematical relationship between a reaction’s rate constant, activation energy, and temperature
- average rate
- rate of a chemical reaction computed as the ratio of a measured change in amount or concentration of substance to the time interval over which the change occurred
- bimolecular reaction
- elementary reaction involving two reactant species
- catalyst
- substance that increases the rate of a reaction without itself being consumed by the reaction
- collision theory
- model that emphasizes the energy and orientation of molecular collisions to explain and predict reaction kinetics
- elementary reaction
- reaction that takes place in a single step, precisely as depicted in its chemical equation
- frequency factor (A)
- proportionality constant in the Arrhenius equation, related to the relative number of collisions having an orientation capable of leading to product formation
- half-life of a reaction (tl/2)
- time required for half of a given amount of reactant to be consumed
- heterogeneous catalyst
- catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur
- homogeneous catalyst
- catalyst present in the same phase as the reactants
- initial rate
- instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)
- instantaneous rate
- rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time
- integrated rate law
- equation that relates the concentration of a reactant to elapsed time of reaction
- intermediate
- species produced in one step of a reaction mechanism and consumed in a subsequent step
- method of initial rates
- common experimental approach to determining rate laws that involves measuring reaction rates at varying initial reactant concentrations
- molecularity
- number of reactant species involved in an elementary reaction
- overall reaction order
- sum of the reaction orders for each substance represented in the rate law
- rate constant (k)
- proportionality constant in a rate law
- rate expression
- mathematical representation defining reaction rate as change in amount, concentration, or pressure of reactant or product species per unit time
- rate law
- (also, rate equation) (also, differential rate laws) mathematical equation showing the dependence of reaction rate on the rate constant and the concentration of one or more reactants
- rate of reaction
- measure of the speed at which a chemical reaction takes place
- rate-determining step
- (also, rate-limiting step) slowest elementary reaction in a reaction mechanism; determines the