activated complex
an unstable arrangement of atoms that exists momentarily at the peak of the activation-energy barrier; an intermediate or transitional structure formed during the course of a reaction
activation energy
the minimum energy colliding particles must have in order to react
chemical equilibrium
a state of balance in which the rates of the forward and reverse reactions are equal; no net change in the amount of reactants and products occurs in the chemical system
collision theory
atoms, ions, and molecules can react to form products when they collide, provided that the particles have enough kinetic energy
common ion
an ion that is common to both salts in a solution; ex: in a solution of silver nitrate and silver chloride, Ag+ would be the _____
common ion effect
a decrease in the solubility of an ionic compound caused by the addition of a common ion
elementary reaction
a reaction in which reactants are converted to products in a single step
entropy
(S) a measure of the disorder of a system; systems tend to go from a state of order (low ___) to a state of maximum disorder (high ___)
equilibrium constant
(Keq) the ratio of product concentrations to reactant concentrations at equilibrium, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation
equilibrium position
the relative concentrations of reactants and products of a reaction that has reached equilibrium; indicated whether the reactants or products are favored in the reversible reaction
first-order reaction
a reaction in which the reaction rate is proportional to the concentration of only one reactant
free energy
the energy available to do work
Gibbs free-energy change
the maximum amount of energy that can be coupled to another process to do useful work
inhibitor
a substance that interferes with the action of a catalyst
intermediate
a product of one of the steps in a reaction mechanism; it becomes a reactant in the next step
law of disorder
it is a natural tendency of systems to move in the direction of maximum chaos or disorder
Le Chatelier's principle
when a stress is applied to a system in dynamic equilibrium, the system changes in a way that relieves the stress
nonspontaneous reaction
a reaction that does not favor the formation of products at the specified conditions
rate
describes the speed of change over an interval of time
rate law
an expression relating the rate of a reaction to the concentration of the reactants
reaction mechanism
a series of elementary reactions that take place during the course of a complex reaction
reversible reaction
a reaction in which the conversion of reactants into products and the conversion of products into reactants occur simultaneously
solubility product constant
(Ksp) an equilibrium constant applied to the solubility of electrolytes; it is equal to the product of the concentrations of the ions each raised to a power equal to the coefficient of the ion in the dissociation equation
specific rate constant
a proportionality constant relating the concentrations of reactants to the rate of the reaction
spontaneous reaction
a reaction that favors the formation of products at the specified conditions; spontaneity depends on enthalpy and entropy changes
transition state
a term sometimes used to refer to the activated complex