General Chemistry: Matter, Stoichiometry, Gases, Thermodynamics, and Acid-Base Equilibria

Comprehensive vocabulary flashcards covering the structure of matter, mass laws, atomic and molecular formulas, nomenclature, gas laws, thermodynamics, and aqueous acid-base equilibria.

Physical Property

A characteristic of a substance that can be observed or measured without altering its chemical identity or nature (e.g., color, density, refractive index, melting point, or boiling point).

Homogeneous System

A system in which physical properties are uniform and identical throughout the entire space it occupies; by definition, it consists of a single phase (e.g., pure water, a salt solution, air).

Heterogeneous System

A system whose physical properties vary across space, consisting of two or more distinct phases (e.g., oil floating on vinegar).

Phase

The collection of all subsystems within a chemical system that exhibit identical physical properties (e.g., water with ice cubes constitutes a two-phase system of a liquid phase and a solid phase).

Emulsion

A heterogeneous mixture in which microscopic droplets of one liquid are suspended in another immiscible liquid (e.g., mayonnaise, milk).

Suspension

A heterogeneous mixture consisting of small solid particles dispersed throughout a liquid medium.

Gel

A two-phase system consisting predominantly of liquid held in place by a solid framework of particles or cross-linked molecules.

Pure Substance

A homogeneous system containing only one chemical component that cannot be separated into simpler substances by physical processes.

Chemical Reaction

A transformation of matter wherein starting substances (reactants) disappear to yield new substances (products) with entirely distinct physical and chemical properties, accompanied by energy exchange.

Element (Simple Substance)

A pure substance consisting of only one type of atom that cannot be chemically decomposed into two or more distinct substances.

Compound (Composite Substance)

A pure substance composed of two or more different elements chemically bonded together that can be broken down into simpler substances via chemical reactions.

Allotropes

Different structural forms of the same chemical element in the same state of aggregation, possessing different physical and chemical properties (e.g., $O_2$ and $O_3$; graphite, diamond, fullerenes, and carbon nanotubes).

Law of Lavoisier

The law of conservation of mass, stating that during a chemical reaction, the total mass of the products formed is always equal to the total mass of the reactants consumed.

Law of Proust

The law of constant composition, stating that the elemental composition of a pure chemical compound is qualitatively and quantitatively constant regardless of its origin or preparation method.

Law of Dalton

The law of multiple proportions, stating that when two elements combine to form more than one compound, the masses of one element that combine with a constant mass of the other are in ratios of small whole numbers.

Einstein's Mass-Energy Equivalence

The principle generalizing mass conservation, given by $\Delta E = c^2\Delta m$, where energy changes during nuclear or chemical reactions correspond to mass changes, with $c = 2.99792458 \times 10^8\,m/s$.

Isotopes

Atoms of the same chemical element having the same atomic number ($Z$) but different mass numbers ($A$) due to a differing number of neutrons ($N$).

Molecule

An electrically neutral structural unit composed of two or more atoms held together by chemical bonds.

Ion

An electrically charged structural unit formed by an atom or group of atoms that has gained electrons (anion, negative charge) or lost electrons (cation, positive charge).

Unit Cell

The smallest repeating structural unit of a crystalline lattice that, by periodic translation in three spatial dimensions, reproduces the entire macroscopic crystal structure.

Metallurgy

The specific domain of chemistry and engineering concerned with the extraction, purification, and processing of metals from their natural ores.

Metal Ores: Malachite, Magnetite, and Cinnabar

Natural mineral ores from which key metals are extracted: malachite yields copper ($Cu$), magnetite yields iron ($Fe$), and cinnabar yields mercury ($Hg$).

Semimetals (Metalloids)

Elements (such as $B$, $Si$, $Ge$, $As$, $Sb$, $Te$) with properties intermediate between metals and non-metals, capable of exhibiting controlled electrical conductivity upon doping.

Empirical Formula

A chemical formula showing the constituent elements of a compound written with subscripts representing the simplest integer ratio of atoms.

Molecular Formula

A chemical formula indicating the exact actual number of atoms of each element comprising one molecule of a molecular substance.

Formula Unit

The empirical representation of an ionic compound showing the simplest integer ratio of cations to anions that maintains overall electrical neutrality.

Valence

The combining capacity of an element, defined as the number of electrons an atom can donate, accept, or share, or the number of univalent bonding partners it can bind.

Relative Atomic Mass ($A_r$)

A dimensionless quantity defined as the ratio of the average absolute mass of an atom of an element to exactly $\frac{1}{12}$ of the absolute mass of a carbon-12 ($^{12}_{6}C$) atom.

Mole

The unit for amount of substance, defined as a quantity of matter containing exactly as many structural entities as there are atoms in exactly $12\,g$ of pure carbon-12 ($^{12}_{6}C$).

Avogadro's Number ($N_0$)

The fundamental constant representing the number of structural units per mole of any chemical substance, equal to $6.0221421 \times 10^{23}\,mol^{-1}$.

Molar Mass ($M$)

The mass in grams of one mole of a substance, expressed in $g\,mol^{-1}$, possessing the same numerical value as its relative formula or molecular mass.

Mole Fraction ($x_i$)

A dimensionless concentration measure defined as the ratio of the amount of substance of component $i$ ($n_i$) to the total amount of all components ($\sum n_j$) in a mixture.

Mass Fraction ($\gamma_i$)

The ratio of the mass of component $i$ ($m_i$) to the total mass of the mixture ($\sum m_j$), often multiplied by $100$ to express mass percent.

Molar Concentration (Molarity)

The concentration measure defined as the amount of dissolved solute in moles divided by the total volume of the solution in liters ($mol\,L^{-1}$ or $\text{M}$).

Ideal Gas

A hypothetical gas whose particles have negligible volume and experience no intermolecular interactions other than perfectly elastic collisions, obeying $PV = nRT$.

Dalton's Law of Partial Pressures

The law stating that the total pressure of a non-reacting gas mixture is equal to the sum of the partial pressures exerted by each individual gas component ($P_{tot} = \sum p_i$), where $p_i = x_i P_{tot}$.

Spectator Ions

Ions in an aqueous solution that do not participate directly in a chemical reaction (e.g., precipitation) and remain unaltered in solution on both sides of the reaction equation.

Internal Energy ($U$)

A state function representing the total microscopic kinetic and potential energy of a thermodynamic system, with changes governed by $\Delta U = q + w$.

Heat Capacity ($C$)

The amount of heat required to raise the temperature of a given sample or unit mass of a substance by one Kelvin, expressed in $J\,g^{-1}\,K^{-1}$ or $J\,mol^{-1}\,K^{-1}$.

State Function

A thermodynamic property whose value depends solely on the current equilibrium state of the system, independent of the path or process taken to reach that state (e.g., $U$, $H$, $S$, $G$).

Enthalpy ($H$)

A thermodynamic state function defined as $H = U + PV$, representing the heat exchanged by a system under constant pressure conditions.

Hess's Law

The principle stating that the standard reaction enthalpy is independent of the pathway and is calculated by $\Delta H^\circ_{reaction} = \sum \alpha \Delta H^\circ_{f,\text{products}} - \sum \beta \Delta H^\circ_{f,\text{reactants}}$.

Entropy ($S$)

A thermodynamic state function that quantifies the molecular disorder or number of microstates of a system, defined for a reversible process as $dS = \frac{dq_{rev}}{T}$.

Gibbs Free Energy ($G$)

A thermodynamic state function defined as $G = H - TS$, whose change indicates the spontaneity of a chemical process at constant temperature and pressure.

Equilibrium Constant ($K$)

The numerical ratio of equilibrium activities or concentrations of products to reactants, related to the standard Gibbs free energy change by $K = e^{-\frac{\Delta G^\circ}{RT}}$.

Autoprotolysis of Water ($K_w$)

The self-ionization reaction of water ($2H_2O \rightleftharpoons H_3O^+ + OH^-$), characterized by the ion-product equilibrium constant $K_w = [H_3O^+][OH^-] = 10^{-14}$ at $25\,^\circ\text{C}$.

Degree of Dissociation ($\alpha$)

The fraction or proportion of original solute molecules that have ionized or dissociated into ions in an electrolyte solution.

Strong Acid

An acid that dissociates completely into ions in aqueous solution, characterized by an acid dissociation constant $K_A \ge 10$.