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All of Chapter 18 (Reaction Rates and Equilibrium) Vocabulary


A measure of the speed of any change that occurs within an interval of time.

Collision Theory

Atoms, ions, and molecules can react to form products when they collide with one another.

Activation Energy

The minimum energy that colliding particles must have in order to react.

Activated Complex

An unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier.

Transition State

Synonym for Activated Complex


A substance that interferes with the action of a catalyst.

Reversible Reaction

One in whih the conversion of reactants to products and the conversion of products to reactants occur simultaneously.

Chemical Equilibrium

When the rates of the forward and reverse reactions are equal, the reaction has reached a state of balance.

Equilibrium Position

Indicates whether the reactants or products are favored in a reversible reaction.

Le Chatelier's Principle

If a stress is applied to a system in dynamic equilibrium, the sytem changes in a way that relieves the stress.

Equilibrium Constant

The ratio of product concentrations to reactant concentrations at equilibrium.

Solubility Product Constant

Equals the product of the concentrations of the ions each raised to a power equalo to the coefficient of the ion in the dissociation equation.

Common Ion

An ion that is found in both salts in a solution.

Common Ion Effect

The lowering of the solubility of an ionic compound as a result of the addition of a common ion.

Free Energy

Energy that is available to do work.

Spontaneous Reaction

Occurs naturally and favors the formation of proudcts at the specified conditions.

Nonspontaneous Reaction

A reaction that does not favor the formation of products at the specified conditions.


A measure of the disorder of a system.

Law of Disorder

States that the natural tendency is for systems to move in the direction of maximum disorer or randomness.

Gibbs Free-Energy Change

The maximum amount of energy that can be coupled to another process to do useful work.

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