AP Chemistry Terms & Concepts

Absorbance

The amount of light that does not pass through a solution

Acidic Buffer

Solution that normally consists of a weak acid and its conjugate base in appreciable and approximately equal concentrations; it buffers a solution in the acidic region of the pH scale

Activation Energy

The minimum kinetic energy that the reacting species much have in order to react

Anion

Any atom of group of atoms with a negative charge

Anode

An electrode where oxidation occurs

Basic Buffer

Solution that has appreciable quantities of both a weak base and its conjugate acid in approximately equal amounts; it buffers a solution in the basic region of the pH scale

Battery

A group of electrochemical cells connected together

Bond Energy

The chemical potential energy able to break a bond

Bronsted-Lowry Acid

A substance or species that donates a hydrogen ion, H+, (a proton)

Bronsted-Lowry Base

A substance or species that accepts a hydrogen ion, H+, (a proton)

Buffer

A solution in which the pH remains relatively constant when small amounts of an acid or base are added

Buffer Capacity

The amount of acid or base a buffer can neutralize before its pH changes significantly

Catalyst

A substance that increases the rates of chemical reactions without being used up

Catalytic Converter

A device that activates several oxidation and?or reduction reactions; usually found in a motor vehicle where a catalyst converts pollutant gases into less-harmful ones

Cathode

The electrode where reduction occurs

Cation

An ion with fewer electrons than protons, giving it a positive charge

Chemical Equillibrium

Condition in which the forward rate of a chemical reaction equals its reverse rate

Chemical Kinetics

The investigation of the rate at which the reactions occur and the factors that affect them

Collision Theory

Theory standing that reaction rates depend on the number of collisions per unit of time, and the fraction of these collisions that succeed in producing products

Conjugate Acid-Base Pair

Two substances that differ by one H+ ion

Electrochemical Cell

A portable source of electricity, in which the electricity is produced by a spontaneous redox reaction within the cell

Electrolysis

Conduction of electricity through a molten electrolyte or an electrolyte solution

Endothermic

A process or reaction in which the system absorbs energy from the surroundings in the form of heat (+△H, heat in the reactants)

Endpoint

The point in a titration at which neutralization is achieved

Enthalpy

The heat content of a system at constant pressure

Entropy

A substance’s or system’s rate of disorganization or randomness (favored at higher temperatures)

Equivalence Point

The point in a titration at which the number of moles of the unknown solution is stoichiometrically equal to the number of moles of the standard solution; the reaction is complete

Exothermic

A process or reaction that releases energy, usually in the form of heat (-△H, heat in the products)

Galvanizing

The process of applying a protective zinc coating to steel or iron to prevent rusting

Half-Reaction

An equation representing either oxidation or reduction, including the number of electrons lost or gained

Electrolyte

A solution the conducts electricity

Electrolytic Cell

An apparatus in which electrolysis occurs

Heterogenous Catalyst

The form of catalysis in which the phase of the catalyst differs from that of the reactants

Heterogenous Reaction

When reactants are present in different states in a reacting system

Homogenous Catalyst

Catalyst that exists in the same phase as the rest of the reaction system

Hydrolysis

The reaction of an ion with water to produce either the conjugate base of the ion and hydronium ions or the conjugate acid of the ion and hydroxide ions

Inhibitor

Substance that reduces the rate of a chemical reaction by combining with a reactant to stop it from reacting in its usual way

Intermediate

A species that is formed in one step and consumed in a subsequent step and so does not appear in the overall reaction

Le Châtelier’s Principle

Principle stating that an equilibrium system subjected to a stress will shift to partially alleviate the stress and restore equillibrium

Overpotential

Increase in potential difference beyond the calculated value for the cell potential

Oxidizing Agent

A substance that accepts electrons in a reaction and therefore oxidizes the other reactant

Rate Law

An expression that links the reaction rate with concentrations or pressures of reactants and constant parameters

Reaction Quotient (Q)

The numerical value derived when any set of reactant and product concentrations are calculated in and equilibrium expression; trial Keq

Reducing Agent

A substance in a redox reaction that donates electrons; in the reaction, the reducing agent is oxidized

Saturated

The point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a separate phase

Shift Left

When a system responds by changing some products into reactants, the response is referred to as a “shift left”

Shift Right

When a system responds by changing some reactants into products, the response is referred to as a “shift right”

Strong Acid

An acid that ionizes nearly 100% in aqueous solution

Strong Base

A base that dissociates nearly 100% in aqueous solution

Weak Acid

An acid that only partially ionizes in aqueous solution

Weak Base

A base that does not dissociate completely in aqueous solution

6 Strong Acids

Perchloric (HCLO4), Hydroiodic (HI), Hydrobromic (HBr), Hydrochloric (HCl), Nitric (HNO3), Sulfuric (H2SO4)

2 Strong Bases

Hydroxide Ion (OH-), Ammonia (NH3)

K(water)

1.0×10^-14

Arrhenius Theory of Acids and Bases

Acids release H+ ions and bases release OH- ions

Phenolphthalein

Indication, pKa = 9.1, basic at color change (str. base + wk. acid titration)

Bromythmol Blue

Indication, pKa = 6.8, neutral at color change (str. acid + str. base titration)

Methyl Red

Indication, pKa = 5.6, acidic at color change (str. acid + wk. base titration)

Rules for Non-Metal and Metal Oxides in Water

1) Non-Metal oxides in water make acids

2) Metal oxides in water make bases

1st Law of Thermodynamics

Law of Conservation of Energy - energy can neither be created nor destroyed, only converted from one form of energy to another

2nd Law of Thermodynamics

Entropy always increases in any reaction that happens “spontaneously”

Faraday’s Constant

1 mol e-’s = 96,000 coul/1 mol e-’s

When are products favored

When K>1

Effects of Conc. on Voltage

1) Voltage increases if conc. of reactants increases

2) Voltage increases if conc. of reactants decreases

Energy for Breaking/Making Bonds

Heat of Bonds Broken - Heat of Bonds Formed