chem ch 12&13 definitions

Chemical kinetics

The field of study dealing with the speed of reactions, or reaction rates, is called

Reaction rate

The speed of a chemical reaction

Instantaneous rate

The rate of the reaction at any particular moment in time

Catalyst

Agents that when added to a reaction mixture increase the reaction rate but do not get used up

Rate law

The expression relating the rate to the concentration of the reactants

Rate constant

The proportionally constant, k

Reaction orders

The values of the exponents are typically small, whole numbers

Overall reaction order

the sum of the reaction orders of each reactant

First-order reaction

One whose rate depends on the concentration of a single reactant with an exponent of one

Second-order reaction

The one in which the rate depends on a single reactant concentration with an exponent of two, or on the concentration of two reactants each with an exponent one

Half-life

The time required for the concentration of a reactant to reach on half of its initial value

Activation energy

The minimum energy that molecules need to posses in order for a reaction to occur

Activated complex or transition state

The arrangement of atoms at the highest energy value

Arrhenius equation,Ea

The number of collisions that occur per unit time, and the fraction of collisions with the proper orientation

Frequency factor, A

Take into account both the frequency of collisions and the probability that the collisions are favorably oriented to undergo a reaction

Reaction mechanism

The detailed, stepwise manner in which the reactants are converted into products through bond breaking and bond formation

Elementary reaction or elementary process

A reaction process that occurs in a single step

Molecularity

The number of molecules involved in the elementary reaction determines molecularity

Unimmolecular

For a reaction involving a single molecule

Bimolecular

A reaction involving the collision between two molecules (same identity or different) colliding to produce a product in a single event

Termolecular

Three or more molecules colliding

Intermediate

the first elementary step produces a product that gets used in the second of later elementary steps. These products are short lived

Rate-determining step

Or

The rate limiting step

The overall rate cannot exceed the rate of the slow step so this slow step

Catalyst

A substance that increases the rate of a reaction but does not undergo a permanent chemical change during this process

Homogeneous catalyst

A catalyst that is in the same phase as the reaction taking place

Heterogeneous catalyst

A catalyst is a different phase