ACS General Chemistry Study Guide Review

Comprehensive vocabulary flashcards covering foundational General Chemistry I and II concepts as per the provided ACS Official Guide notes.

Isotope

Atoms of the same element that have the same number of protons but differing numbers of neutrons.

Atomic Number ($Z$)

The number of protons in the nucleus of an atom.

Mass Number ($A$)

The sum of the number of protons and the number of neutrons in an atom's nucleus.

Ion

A chemical species with a net charge because the number of protons and electrons are not equal.

Mole

The amount of substance containing Avogadro's number ($6.022 \times 10^{23}$) of particles.

Avogadro's Number

$6.022 \times 10^{23}$ items per mole.

Empirical Formula

The simplest whole-number ratio of atoms of each element present in a compound.

Molecular Formula

A formula giving the actual number of atoms of each element in a molecule.

Limiting Reactant

The reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product formed.

Theoretical Yield

The maximum mass or amount of product that can be produced in a chemical reaction based on stoichiometry.

Significant Figures

Digits in a measurement that carry meaning contributing to its precision, including one estimated digit.

Density

The ratio of the mass of a substance to the volume it occupies ($d = \frac{m}{V}$).

Strong Electrolyte

A substance that dissociates or ionizes completely into ions when dissolved in water, conducting electricity well.

Weak Electrolyte

A substance that only partially ionizes in water, conducting electricity poorly.

Molar Concentration (Molarity)

The number of moles of solute per cubic decimeter ($dm^3$) of solution.

Precipitate

An insoluble solid that forms and settles out of a liquid mixture during a chemical reaction.

Net Ionic Equation

A chemical equation that shows only those species directly involved in the reaction, excluding spectator ions.

Spectator Ion

An ion that exists in the same form on both the reactant and product sides of a chemical reaction and does not participate in the reaction.

Oxidation

The loss of electrons or an increase in the oxidation number of an atom.

Reduction

The gain of electrons or a decrease in the oxidation number of an atom.

Oxidizing Agent

The substance that accepts electrons and is reduced in a redox reaction.

Reducing Agent

The substance that donates electrons and is oxidized in a redox reaction.

Specific Heat Capacity

The amount of heat energy required to raise the temperature of one gram of a substance by one Kelvin ($J\,g^{-1}\,K^{-1}$).

Enthalpy ($H$)

A thermodynamic property related to the heat content of a system at constant pressure.

Hess's Law

The principle stating that the total enthalpy change for a chemical reaction is the same regardless of the number of steps in the pathway.

Exothermic Process

A process that releases heat to its surroundings (\Delta H < 0).

Endothermic Process

A process that absorbs heat from its surroundings (\Delta H > 0).

First Law of Thermodynamics

Energy can be converted from one form to another but cannot be created or destroyed ($\Delta E = q + w$).

Lattice Energy

The energy required to separate one mole of a solid ionic compound into its gaseous ions.

Electronegativity

A measure of the ability of an atom in a chemical compound to attract shared electrons.

Formal Charge

The charge assigned to an atom in a molecule, assuming electrons in chemical bonds are shared equally between atoms.

Resonance Structure

One of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure.

Bond Enthalpy

The energy required to break a particular bond in one mole of gaseous molecules.

Sigma ($\sigma$) Bond

A covalent bond formed by the head-on overlap of atomic orbitals along the internuclear axis.

Pi ($\pi$) Bond

A covalent bond formed by the side-to-side overlap of parallel p-orbitals.

Hybridization

The concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds.

Bond Order

One-half the difference between the number of bonding electrons and anti-bonding electrons.

Paramagnetic

A substance that is attracted by a magnetic field, usually due to the presence of unpaired electrons.

Diamagnetic

A substance that is not attracted (and is slightly repelled) by a magnetic field because all its electrons are paired.

Ideal Gas Law

The equation of state of a hypothetical ideal gas ($PV = nRT$).

Partial Pressure

The pressure that one component of a gas mixture would exert if it were alone in the container.

Hydrogen Bonding

A strong dipole-dipole attraction that occurs between molecules in which hydrogen is bonded to N, O, or F.

Vapor Pressure

The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature.

Critical Point

The temperature and pressure above which a substance exists as a supercritical fluid and cannot be liquefied.

Triple Point

The unique temperature and pressure at which all three phases (solid, liquid, and gas) of a substance coexist in equilibrium.

Molality ($m$)

The number of moles of solute per kilogram of solvent ($mol\,kg^{-1}$).

Mole Fraction ($X$)

The ratio of the number of moles of one component of a mixture to the total number of moles of all components.

Colligative Properties

Properties of a solution that depend only on the number of solute particles, not their identity (e.g., boiling point elevation).

Reaction Rate

The change in concentration of a reactant or product per unit time.

Rate Law

An expression relating the rate of a reaction to the concentrations of the reactants raised to specific powers.

Half-life ($t_{1/2}$)

The time required for the concentration of a reactant to decrease to half of its initial concentration.

Activation Energy ($E_a$)

The minimum amount of energy required to start a chemical reaction.

Catalyst

A substance that increases the rate of a chemical reaction byProviding an alternative pathway with a lower activation energy, without being consumed.

Reaction Mechanism

The sequence of elementary steps that lead to the overall chemical change.

Chemical Equilibrium

The state in which the rates of the forward and reverse reactions are equal, and concentrations remain constant.

Equilibrium Constant ($K$)

The ratio of the product concentrations to reactant concentrations at equilibrium, each raised to the power of their coefficients.

Reaction Quotient ($Q$)

A measure of the relative amounts of products and reactants present in a reaction at a given time ($Q$ is compared to $K$).

Le Chatelier's Principle

If a system at equilibrium is disturbed, the system will shift its equilibrium position to counteract the effect of the disturbance.

Bronsted-Lowry Acid

A substance that can donate a proton ($H^+$) to another substance.

Bronsted-Lowry Base

A substance that can accept a proton ($H^+$) from another substance.

Conjugate Acid-Base Pair

Two species that differ only by the presence or absence of a single proton ($H^+$).

Lewis Acid

A substance that can accept a pair of electrons to form a covalent bond.

Lewis Base

A substance that can donate a pair of electrons to form a covalent bond.

Buffer

A solution that resists changes in pH when small amounts of acid or base are added, typically containing a weak acid and its conjugate base.

pH

The negative base-10 logarithm of the hydronium ion concentration ($pH = -\log[H_3O^+]$).

Molar Solubility

The number of moles of solute in one cubic decimeter ($dm^3$) of a saturated solution.

Solubility Product Constant ($K_{sp}$)

The equilibrium constant for the dissolution of a solid ionic compound in water.

Common Ion Effect

The reduction in the solubility of an ionic compound due to the presence of a soluble salt that contains an ion in common with the compound.

Entropy ($S$)

A thermodynamic measure of the dispersal of energy or the degree of disorder/randomness in a system.

Gibbs Free Energy ($G$)

A thermodynamic state function used to predict the spontaneity of a process at constant temperature and pressure ($\Delta G = \Delta H - T\Delta S$).

Spontaneous Process

A process that occurs without external intervention, characterized by a negative change in Gibbs free energy (\Delta G < 0).

Standard Molar Entropy ($S^\circ$)

The entropy of one mole of a substance at standard state conditions (usually $298\,K$ and $1\,atm$).

Galvanic (Voltaic) Cell

An electrochemical cell that uses a spontaneous chemical reaction to generate electricity.

Electrolytic Cell

An electrochemical cell that uses electrical energy to drive a non-spontaneous chemical reaction.

Anode

The electrode in an electrochemical cell where oxidation occurs.

Cathode

The electrode in an electrochemical cell where reduction occurs.

Salt Bridge

A pathway constructed to allow the passage of ions from one side of an electrochemical cell to the other to maintain electrical neutrality.

Standard Reduction Potential ($E^\circ$)

The voltage associated with a reduction half-reaction at an electrode under standard state conditions.

Faraday Constant ($F$)

The magnitude of electric charge per mole of electrons ($96485\,C\,mol^{-1}$).

Nernst Equation

An equation relating the potential of an electrochemical cell to the standard cell potential and the concentrations/pressures of the reactants and products.

Alpha (\alpha) Particle

A helium nucleus ($^4_2He$) emitted during radioactive decay.

Beta (\beta) Particle

A high-speed electron ($^0_{-1}e$) emitted from the nucleus during radioactive decay.

Gamma (\gamma) Ray

High-energy electromagnetic radiation emitted from an atomic nucleus during radioactive decay.

Nuclear Fission

A nuclear reaction in which a heavy nucleus splits into smaller nuclei with the simultaneous release of energy and neutrons.

Nuclear Fusion

A nuclear reaction in which light nuclei combine to form a heavier nucleus with the release of large amounts of energy.

Positron Emission

A type of radioactive decay in which a proton in the nucleus is converted into a neutron and a positron ($^0_{+1}e$) is emitted.

Electron Capture

A process in which an inner-shell electron is captured by the nucleus, converting a proton into a neutron.

Nuclear Transmutation

The conversion of one chemical element or isotope into another element through a nuclear reaction.

Effective Nuclear Charge ($Z_{eff}$)

The net positive charge experienced by valence electrons, calculated as the actual nuclear charge minus the shielding effect of inner electrons.

Ionization Energy

The minimum energy required to remove an electron from a gaseous atom or ion in its ground state.

Electron Affinity

The energy change that occurs when an electron is added to a gaseous atom.

Valence Electrons

Electrons in the outermost energy level (shell) of an atom that participate in chemical bonding.

Atomic Radius

One-half the distance between the nuclei of identical atoms that are bonded together (decreases across a period, increases down a group).

Ionic Radius

The radius of an atom's ion (cations are smaller than parent atoms; anions are larger).

Principal Quantum Number ($n$)

The quantum number that indicates the main energy level or shell of an electron.

Angular Momentum Quantum Number ($\ell$)

The quantum number that defines the shape of an orbital ($s, p, d, f$).

Magnetic Quantum Number ($m_\ell$)

The quantum number that describes the orientation of an orbital in space.

Spin Quantum Number ($m_s$)

The quantum number that describes the intrinsic angular momentum (spin) of an electron ($+1/2$ or $-1/2$).

Photon

A particle representing a quantum of light or other electromagnetic radiation.

Wavelength (\lambda)

The distance between identical points on consecutive cycles of a wave.