AP Chemistry Review Vocabulary (Concentration, Stoichiometry, Formulas, and Basic Concepts)

Vocabulary flashcards covering key concepts from lecture notes pages 1–13.

Molarity

Concentration of a solution expressed as moles of solute per liter of solution (mol/L).

Dilution

Process of lowering solution concentration by adding solvent; moles of solute stay the same.

Concentrated Solution

A solution with a high molarity; typically used before dilution.

Theoretical Yield

Maximum amount of product that can be produced from given reactants based on stoichiometry and limiting reactant.

Limiting Reactant

The reactant that limits the amount of product formed in a reaction; others are in excess.

Percent Yield

Actual yield divided by theoretical yield, expressed as a percentage.

Stoichiometry

Quantitative relationships between reactants and products in a balanced chemical equation.

Balancing Equations

Process of equalizing atoms on both sides of a chemical equation using coefficients.

Skeletal Equation

An unbalanced equation showing reactants and products with their formulas.

Coefficients vs Subscripts

Coefficients balance equations; subscripts are part of the chemical formula and should not be changed to balance.

Empirical Formula

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

Molecular Formula

The actual number of each type of atom in a molecule.

Percent Composition

The percent by mass of each element in a compound.

Molar Mass

Mass of one mole of a substance (g/mol); numerically equal to the element’s atomic mass in amu.

Avogadro’s Number

6.022 × 10^23 representative units per mole.

Atomic Number (Z)

Number of protons in the nucleus; equals the number of electrons in a neutral atom.

Mass Number (A)

Sum of protons and neutrons in the nucleus.

Isotopes

Atoms of the same element with different numbers of neutrons.

Natural Abundance

Relative proportion of isotopes found in a naturally occurring sample.

Protons

Positively charged subatomic particles; define the element (Z).

Neutrons

Electrically neutral subatomic particles; contribute to atomic mass.

Electrons

Negatively charged subatomic particles; balance protons in neutral atoms.

Atomic Mass Unit (AMU)

Unit used to express atomic and molecular masses; 1 u ≈ 1/12 the mass of a carbon-12 atom.

Law of Conservation of Mass

Matter cannot be created or destroyed in a chemical reaction; mass is conserved.

Constant Composition (Definite Proportions)

A given compound has fixed elemental ratios by mass, regardless of sample source.

Multiple Proportions

When two elements form more than one compound, the masses of one element that combine with a fixed amount of the other are in small whole-number ratios.

Atomic Theory (Four Postulates)

(1) Elements are made of atoms; (2) Atoms of a given element have the same mass; (3) Atoms combine in simple whole-number ratios; (4) Atoms cannot be created or destroyed in a chemical reaction.

Law of Definite vs Law of Multiple Proportions

Definite proportions: fixed ratio in a compound; Multiple proportions: different compounds have ratios of elements as small whole numbers.

Chemical Properties

Properties observed only by changing the chemical composition (e.g., flammability, acidity).

Physical Properties

Properties observed without changing the substance’s composition (e.g., odor, color, density).

Pure Substance

Contains only one type of substance (element or compound).

Mixture

Contains two or more pure substances in any ratio.

Element

A substance consisting of only one type of atom.

Compound

A substance made of two or more different elements in a fixed ratio.

Homogeneous Mixture

Uniform composition throughout the sample.

Heterogeneous Mixture

Non-uniform composition; different parts have different properties.

Diatomic Elements

Elements that exist naturally as diatomic molecules (e.g., O2, N2, H2).

Acids: Binary and Oxyacids

Binary acids consist of hydrogen and a nonmetal (e.g., HCl); oxyacids contain hydrogen and an oxyanion (e.g., H2SO3).

Alcohols and Carboxylic Acids

Alcohols contain the hydroxyl group (-OH); carboxylic acids contain the carboxyl group (-COOH).

Alkanes, Alkenes, Alkynes

Hydrocarbons with single bonds (alkanes), double bonds (alkenes), or triple bonds (alkynes).

Empirical to Molecular Formula Relationship

Empirical formula gives the simplest ratio; molecular formula is determined by molar mass.

SI Prefixes (nano, micro, milli, centi, kilo)

Prefixes used to express powers of ten (e.g., nano 10^-9, micro 10^-6, milli 10^-3, centi 10^-2, kilo 10^3).