General Chemistry II: Ch 17-20 (Exam 2)

as of 7/24 only includes up to chapter 18

Activation Energy (Ea)

The minimum energy required for a reaction to occur. Forward and reverse reactions generally have different activation energies.

Activity

A unitless measure of the effective concentration of a species. In these notes, it is numerically equal to molar concentration for aqueous species, pressure for gases, and 1 for pure solids and pure liquids.

Activity of an Aqueous Species

The ratio of an aqueous species' molar concentration to the standard concentration of 1 M.

Activity of a Gas

The ratio of a gas's pressure to the standard pressure of 1 atm.

Arrhenius Equation

The equation k=Ae^(−Ea/RT), which relates the rate constant to temperature and activation energy.

Arrhenius Plot

A graph of ln⁡k\ln klnk versus 1/T; its slope equals −Ea/R.

Catalyst

A substance that increases the rates of both the forward and reverse reactions equally without changing the equilibrium constant or the equilibrium position.

Chemical Equilibrium

The state in which the forward and reverse reactions occur at the same rate, resulting in constant concentrations of reactants and products.

Combining Equilibria

When chemical equations are added together, their equilibrium constants are multiplied.

Concentration Stress

A disturbance caused by adding or removing reactants or products, causing the equilibrium position to shift.

Coupled Equilibria

Multiple equilibrium reactions that share one or more chemical species and whose equilibrium constants can be combined mathematically.

Direction of Reaction

The direction (forward or reverse) in which a reaction proceeds to reach equilibrium, determined by comparing Q and K.

Dynamic Equilibrium

An equilibrium in which the forward and reverse reactions continue to occur even though there is no net change in observable properties.

Endothermic Reaction

A reaction that absorbs heat. Increasing the temperature shifts the equilibrium toward the products.

Equilibrium Constant (K)

A dimensionless constant that describes the ratio of product activities to reactant activities at equilibrium for a given reaction and temperature.

Equilibrium Constant Expression

The mathematical expression for KKK, written as the ratio of product activities to reactant activities, each raised to its stoichiometric coefficient.

Equilibrium Position

The relative amounts of reactants and products present when equilibrium has been established.

Equilibrium Shift

A change in the position of equilibrium caused by an external disturbance.

Exothermic Reaction

A reaction that releases heat. Increasing the temperature shifts the equilibrium toward the reactants.

Extent of Reaction

The degree to which reactants are converted into products before equilibrium is reached.

Forward Reaction

The reaction that converts reactants into products.

ICE Table

A table (Initial, Change, Equilibrium) used to organize information and solve equilibrium concentration or pressure problems.

Law of Mass Action

The principle stating that the equilibrium constant expression is the ratio of product activities to reactant activities, each raised to its stoichiometric coefficient.

Le Châtelier's Principle

If a system at equilibrium is disturbed, it shifts in the direction that partially opposes the disturbance.

Magnitude of K

Indicates whether products or reactants are favored at equilibrium. Large K favors products; small K favors reactants.

Pressure Stress

A disturbance caused by changing the pressure or volume of a gaseous equilibrium system.

Product

A substance appearing on the right side of a chemical equation and produced in the forward reaction.

Pure Liquid

A liquid whose activity is defined as 1; therefore, it is omitted from equilibrium constant expressions.

Pure Solid

A solid whose activity is defined as 1; therefore, it is omitted from equilibrium constant expressions.

Reaction Quotient (Q)

The ratio of product activities to reactant activities calculated using current (non-equilibrium) concentrations or pressures.

Reactant

A substance appearing on the left side of a chemical equation and consumed in the forward reaction.

Reverse Reaction

The reaction that converts products back into reactants.

Reversing an Equation

Reversing a balanced chemical equation changes the equilibrium constant to its reciprocal (1/K).

Scaling a Reaction

Multiplying every coefficient in a balanced chemical equation by a constant raises the equilibrium constant to that same power.

Standard State

The reference state used to define activities (1 M for aqueous species, 1 atm for gases, and the pure substance for solids and liquids).

Stress

Any change in concentration, pressure, temperature, or another condition that disturbs a system at equilibrium.

Temperature Stress

A disturbance caused by changing the temperature, which affects the forward and reverse reaction rates differently and shifts the equilibrium position.

Thermodynamic Equilibrium Constant

The equilibrium constant based on activities rather than concentrations or pressures alone.

Kc

The equilibrium constant expressed using concentration terms only. (DO NOT CALCULATE FOR THIS ON EXAMS/QUIZZES)

Kp

The equilibrium constant expressed using pressure terms only for gaseous species. (DO NOT CALCULATE FOR THIS ON EXAMS/QUIZZES)

Acid–base indicator

A substance that changes color over a specific pH range to indicate whether a solution is acidic or basic.

Acid-dissociation (acid-ionization) constant (Ka)

The equilibrium constant that measures the strength of a weak acid by describing the extent of its ionization in water.

Adduct

A compound formed when a Lewis acid and a Lewis base join together by sharing an electron pair.

Amphiprotic

A substance that can act as either a proton donor (acid) or a proton acceptor (base), depending on the reaction.

Arrhenius acid

A substance that increases the concentration of hydrogen ions (H⁺ or H₃O⁺) when dissolved in water.

Arrhenius base

A substance that increases the concentration of hydroxide ions (OH⁻) when dissolved in water.

Autoionization

The process in which water molecules react with each other to produce hydronium ions (H₃O⁺) and hydroxide ions (OH⁻).

Base-dissociation (base-ionization) constant (Kb)

The equilibrium constant that measures the strength of a weak base by describing the extent of its reaction with water.

Brønsted–Lowry acid–base definition

A theory stating that acids are proton donors and bases are proton acceptors.

Conjugate acid–base pair

Two species that differ by the gain or loss of a single proton (H⁺).

Hydronium ion (H₃O⁺)

The ion formed when a water molecule accepts a proton (H⁺).

Ion-product constant for water (Kw)

The equilibrium constant for the autoionization of water, equal to [H3O+][OH−]

Leveling effect

The phenomenon in which all strong acids or all strong bases appear equally strong in a given solvent because they react completely with that solvent.

Lewis acid–base definition

A theory stating that Lewis acids accept an electron pair and Lewis bases donate an electron pair.

Neutralization

An acid–base reaction in which an acid and a base react to produce water and a salt.

pH

A logarithmic measure of the hydrogen ion concentration of a solution, defined as pH=−log⁡[H+]

Polyprotic acid

An acid capable of donating two or more protons (H⁺) per molecule.

Proton acceptor

A Brønsted–Lowry base that accepts a proton (H⁺) during a chemical reaction.

Proton donor

A Brønsted–Lowry acid that donates a proton (H⁺) during a chemical reaction.