Kinetics

Intermediates

Species made in one step and used in another; they do not appear in the overall equation.

Slow Step

The step in a reaction mechanism that determines the rate law.

Rate Law

An expression that relates the rate of a reaction to the concentration of its reactants.

Catalysts

Substances that increase the rate of reaction by lowering activation energy, appearing at the start and reappearing at the end.

Zero Order Reaction

A reaction where the rate is constant and does not depend on the concentration of reactants.

First Order Reaction

A reaction where the rate is proportional to the concentration of one reactant.

Second Order Reaction

A reaction where the rate is proportional to the square of the concentration of one reactant.

Half-life

The time required for the concentration of a reactant to decrease to half its initial concentration, constant only for first-order reactions.

Rate Constant (k)

A constant that indicates the speed of a reaction, affected only by temperature or catalysts.

Collision Theory

A theory stating that for a reaction to occur, reactant particles must collide with sufficient energy and proper orientation.

Activation Energy (Ea)

The minimum energy that must be overcome for a reaction to occur.

Homogeneous Catalyst

A catalyst that exists in the same phase as the reactants.

Heterogeneous Catalyst

A catalyst that exists in a different phase than the reactants.

Effective Collisions

Collisions that result in a reaction due to having sufficient energy and correct orientation.

Stoichiometry vs Rate Law

In elementary steps, stoichiometric coefficients indicate reaction order; for overall reactions, only experimental data reveals the order.

Substitution of Intermediates

The process of replacing an intermediate in the rate law with its corresponding reactants.

Graph of Zero Order Kinetics

A plot of [A] versus time that yields a straight line with a slope of -k.

Graph of First Order Kinetics

A plot of ln[A] versus time that yields a straight line with a slope of -k.

Graph of Second Order Kinetics

A plot of 1/[A] versus time that yields a straight line with a slope of +k.