Honors Chemistry Kinetics Flashcards

Vocabulary terms and definitions covering chemical kinetics, collision theory, factors affecting reaction rates, and rate law expressions as presented in the lecture notes.

Chemical Kinetics

Area of chemistry concerned with the speeds, or rates, at which a chemical reaction occurs.

Reaction Rate

The change in the concentration of a reactant or a product with time, measured in concentration units (molarity, $M$) per second, ($M/s$).

Collision Theory of Kinetics

A theory assuming particles collide perfectly elastically, stating a reaction takes place only when molecules collide with the proper orientation and sufficient energy.

Rate Expression

Equality that relates the rate of each substance in a chemical reaction; reactants are given a negative sign because they disappear.

Activation Energy ($E_a$)

Minimum energy that colliding particles must have in order to have a reaction; it represents the energy required to break bonds when reactants collide.

Transition State ($AB^{\ddagger}$)

Temporary substance formed by the collision of reactant molecules before the product(s) is formed; also known as an intermediate or activated complex.

Catalyst

Substance that increases the reaction rate by lowering the activation energy barrier; it provides an alternate reaction pathway and is not consumed during the reaction.

Rate Law

Expresses the relationship between reaction rate and the concentration of the reactant, represented by the expression $\text{Rate} = k[A]^n$.

Rate Constant ($k$)

Proportionality that describes the relationship between the rate of a reaction and the concentration of reactants; its units depend on the order of the reaction.

Reaction Order

The power to which a reactant concentration in the rate law is raised; it determines how the rate depends on the [reactant] and must be determined experimentally.

Overall Reaction Order

The sum of the exponential powers for all reactant concentrations appearing in the rate law ($x + y$).

Zero Order Reaction

Reactions whose overall order is zero and are independent of reactant concentration; the rate is the same at all concentrations.

First Order Rate Law

Reactions whose overall order is one and is directly proportional to reactant concentration; doubling concentration doubles ($2\times$) the rate.

Second Order Rate Law

Reactions whose overall order is two and is proportional to reactant concentration squared; doubling concentration quadruples ($4\times$) the rate.

Arrhenius Equation

Expresses the dependence of the rate constant ($k$) of a reaction on temperature: $k = Ae^{-E_a/RT}$.

Surface Area

The sum of the exposed sides area in the solid state; larger surface area leads to a faster reaction rate by exposing more reactants for collisions.

Agitation

Force applied to move components (stirring) which increases the rate of reaction by moving reactants and increasing collisions.

Enthalpy of RXN ($\Delta H$)

The enthalpy change of a system calculated as $\Delta H = H_{\text{products}} - H_{\text{reactants}}$; it is negative for exothermic reactions and positive for endothermic processes.