Chapter 7: Chemical Reactions - Energy, Rates, and Equilibrium

Vocabulary practice flashcards covering thermodynamics, reaction kinetics, chemical equilibrium, and Le Chatelier's principle based on Chapter 7 lecture notes.

Energy

The capacity to supply heat or do work.

Work ($w$)

The process of causing matter to move against an opposing force.

Potential Energy

The energy an object possesses because of its relative position, composition, or condition; often referred to as stored energy.

Kinetic Energy

The energy that an object possesses because of its motion.

Law of Conservation of Energy

The principle stating that during a chemical or physical change, energy can be neither created nor destroyed, although it can be changed in form.

Bond Dissociation Energy

The characteristic quantity of energy required to break a specific chemical bond and separate a molecule into individual atoms.

Lattice Energy

The term used to describe the bond energy or strength of attraction between oppositely charged ions in ionic compounds.

Heat of Reaction ($\Delta H$)

The measured difference between the total heat absorbed and the total heat released during a chemical reaction performed at constant pressure; also called enthalpy change.

Endothermic Reaction

A chemical reaction that absorbs energy or heat from its surroundings, characterized by a positive enthalpy change ($\Delta H > 0$).

Exothermic Reaction

A chemical reaction that releases energy or heat to its surroundings, characterized by a negative enthalpy change ($\Delta H < 0$).

Spontaneous Reaction

A reaction that favors the formation of products under the specific conditions in which the reaction is occurring.

Nonspontaneous Reaction

A reaction that does not favor the formation of products under a given set of conditions.

Entropy ($S$)

The tendency in nature for systems to proceed toward a state of greater disorder or randomness, expressed in units of $\text{J}/(\text{mol}\cdot\text{K})$.

Free Energy ($G$)

Energy that is available to do work, determined by a mathematical combination of the enthalpy change, entropy change, and absolute temperature ($\Delta G = \Delta H - T\Delta S$).

Exergonic

A term used in living systems to describe a process or chemical reaction that releases free energy, characterized by $-\Delta G$.

Endergonic

A term used in living systems to describe a process or chemical reaction that requires or absorbs free energy, characterized by $+\Delta G$.

Chemical Kinetics

The study of the speeds or rates of chemical reactions.

Reaction Rate

The change in concentration of a reactant or product with time, typically measured in units of molarity per second ($\text{M/s}$).

Collision Theory

A set of principles stating that reactant particles form products when they collide with sufficient kinetic energy and the correct orientation.

Activation Energy ($E_a$)

The minimum energy that colliding particles must possess in order to overcome the energy barrier and undergo a chemical reaction.

Activated Complex

An unstable arrangement of atoms that exists momentarily at the peak of the activation energy barrier on a potential energy curve.

Potential Energy Diagram

A diagram, also known as a reaction progress curve, that illustrates the change in potential energy of a chemical system as reactants convert into products.

Catalyst

A substance that accelerates the rate of a chemical reaction without being consumed by providing an alternative reaction pathway with a lower activation energy barrier.

Reversible Reaction

A chemical reaction that can proceed in either the forward or the reverse direction.

Chemical Equilibrium

The point in a reversible reaction at which the forward and reverse processes balance each other's progress, proceeding at identical rates so that concentrations remain constant.

Law of Mass Action

The observation relating the amounts of reactants and products at equilibrium, establishing that a specific ratio of products to reactants is achieved at equilibrium.

Equilibrium Constant ($K_{eq}$)

A characteristic numerical value for a given reaction at a specified temperature, defined as the ratio of equilibrium concentrations of products to reactants, with each raised to the power of its stoichiometric coefficient.

Pressure-Based Equilibrium Constant ($K_P$)

An equilibrium constant expression defined for gas-phase reactions using the equilibrium partial pressures of reactants and products in atmospheres.

Heterogeneous Equilibrium

An equilibrium system that involves reactants and products present in more than one phase of matter.

Le Chatelier’s Principle

The principle stating that if a chemical equilibrium is stressed, the reaction shifts in a direction that reduces the stress.