Rate of Reaction- a measure of the rate at which reactants are used up or the rate at which products are formed; the units of rate are mol*/((dm^3)s), rate = (change in amount of reactants/products)/ (time).

Collision Theory- In order to react w/ e/o, particles must collide in the correct orientation and w/ sufficient energy, the particles may be atoms, ions, or molecules.

Activation Energy- the minimum energy that colliding particles must possess for successful collision that results in a reaction to take place, denoted E[subscript a].

Catalyst- A substance that increases the rate of a reaction but remains chemically unchanged itself at the end of the reaction.

Boltzmann Distribution- A graph showing the distribution of energies of the particles in a sample at a given temperature.

Enzyme- A protein molecule that is a biological catalyst; most act on a specific substrate.

Substrate- A molecule that fits into the active site of an enzyme and reacts.

(Chapter 22 begins)

Rate constant- The proportionality constant in the rate equation, denoted k.

Rate Equation- An equation showing the relationship between the rate constant and the concentration of those reactants that affect the rate of reaction; the general form of the equation is: rate=k([A]^m)([B]^n) where k is the rate constant, [A] and [B] are the concentrations of those reactants that affect the rate of reaction, m is the order of the reaction w/ respect to A and n is the order of reaction w/ respect to B.

Order of Reaction- The power to which the concentration of a reactant is raised in the rate equation; if the concentration does not affect the rate, the reaction is zero order; if the rate is directly proportional to the reactant concentration, the reaction is first order; if the rate is directly proportional to the square of the reactant concentration, the reaction is second order.

Half Life (t[subscript 1/2])- The time taken for the amount (or concentration) of the limiting reactant in a reaction to decrease to half its value.

Rate Determining Step- The slowest step in a reaction mechanism.

Homogeneous Catalyst- The type of catalysis in which the catalyst and reactants are in the same phase; for example, sulfuric acid catalyzing the formation of an ester from an alcohol and carboxylic acid (both reactants liquid).

Heterogeneous Catalyst- The type of catalysis in which the catalyst is in a different phase from the reactants, for example, iron in the Haber process.

Adsorption (in catalysis)- The first stage in heterogeneous catalysis; molecules of reactants (usually gases) form bonds with atoms on the surface of the catalyst.

Desorption- The last stage in heterogeneous catalysis; the bonds holding the molecule(s) of product(s) to the surface of the catalyst are broken and the product molecules diffuse away from the surface of the catalyst.

Instantaneous Rate of Change- The rate of reaction at any particular point in time.