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AP Chemistry Key Terms

Vocabulary and relationships from atomic structure to equilibrium, kinetics and thermodynamics.

106 cardsGrades 9–12, College#ap#chemistry

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  • MoleTerm
    6.022 x 10^23 particles; the chemist's counting unit
  • Avogadro's numberTerm
    6.022 x 10^23 per mole
  • Molar massTerm
    Mass in grams of one mole of a substance
  • Empirical formulaTerm
    The simplest whole-number ratio of atoms
  • Molecular formulaTerm
    The actual number of each atom in a molecule
  • Percent compositionTerm
    Mass percent of each element in a compound
  • Limiting reactantTerm
    The reactant that runs out first and caps the product
  • Theoretical yieldTerm
    The maximum product predicted by stoichiometry
  • Percent yieldTerm
    (actual yield / theoretical yield) x 100
  • MolarityTerm
    Moles of solute per liter of solution
  • Dilution equationTerm
    M1V1 = M2V2
  • IsotopeTerm
    Atoms of one element with different numbers of neutrons
  • Average atomic massTerm
    Weighted average of an element's isotopes
  • Mass spectrometryTerm
    Measures isotope masses and abundances
  • Photoelectron spectroscopyTerm
    Measures energies needed to remove electrons from atoms
  • Electron configurationTerm
    Arrangement of electrons in orbitals
  • Aufbau principleTerm
    Fill lowest-energy orbitals first
  • Pauli exclusion principleTerm
    No two electrons in an atom share all four quantum numbers
  • Hund's ruleTerm
    Fill degenerate orbitals singly before pairing
  • Valence electronsTerm
    Outer-shell electrons involved in bonding
  • Effective nuclear chargeTerm
    Net pull felt by outer electrons
  • Atomic radius trendTerm
    Decreases across a period, increases down a group
  • Ionization energy trendTerm
    Generally increases across a period, decreases down a group
  • ElectronegativityTerm
    An atom's pull on shared electrons in a bond
  • Coulomb's lawTerm
    Force depends on charges and decreases with distance squared
  • Ionic bondTerm
    Attraction between oppositely charged ions
  • Covalent bondTerm
    A shared pair of electrons
  • Metallic bondTerm
    Positive ions in a sea of delocalized electrons
  • Lattice energyTerm
    Energy released when gaseous ions form an ionic solid
  • Bond orderTerm
    Number of bonding pairs between two atoms
  • Bond length trendTerm
    Higher bond order means shorter, stronger bonds
  • Lewis structureTerm
    A diagram of valence electrons and bonds
  • Formal chargeTerm
    Valence electrons minus nonbonding electrons minus half the bonding electrons
  • ResonanceTerm
    Multiple valid Lewis structures for one species
  • VSEPR theoryTerm
    Electron groups arrange to minimize repulsion
  • Linear geometryTerm
    Two electron groups; 180 degrees
  • Trigonal planarTerm
    Three electron groups; 120 degrees
  • TetrahedralTerm
    Four electron groups; 109.5 degrees
  • Hybridization sp3Term
    Four electron groups, tetrahedral
  • Sigma bondTerm
    Head-on overlap of orbitals
  • Pi bondTerm
    Side-by-side overlap of p orbitals
  • Polar bondTerm
    A bond with unequal sharing
  • London dispersion forcesTerm
    Weak attractions from temporary dipoles; present in all molecules
  • Dipole-dipole forceTerm
    Attraction between polar molecules
  • Hydrogen bondingTerm
    Strong dipole attraction involving H bonded to N, O or F
  • Ideal gas lawTerm
    PV = nRT
  • Combined gas lawTerm
    P1V1/T1 = P2V2/T2
  • Dalton's lawTerm
    Total pressure is the sum of partial pressures
  • Kinetic molecular theoryTerm
    Gas particles move randomly with energy proportional to temperature
  • Graham's lawTerm
    Lighter gases effuse faster
  • Real gas deviationTerm
    Gases act least ideally at high pressure and low temperature
  • SoluteTerm
    The substance dissolved
  • SolventTerm
    The substance doing the dissolving
  • ElectrolyteTerm
    A substance that forms ions in water and conducts
  • Net ionic equationTerm
    Shows only the species that change, omitting spectators
  • Spectator ionTerm
    An ion unchanged by a reaction
  • PrecipitateTerm
    An insoluble solid formed in solution
  • Beer-Lambert lawTerm
    Absorbance is proportional to concentration: A = abc
  • OxidationTerm
    Loss of electrons
  • ReductionTerm
    Gain of electrons
  • Oxidizing agentTerm
    The species that is reduced
  • Reducing agentTerm
    The species that is oxidized
  • Rate lawTerm
    Equation relating reaction rate to concentrations
  • Reaction orderTerm
    The exponent of a reactant in the rate law
  • Rate constantTerm
    The proportionality constant k in the rate law
  • First-order half-lifeTerm
    ln 2 / k; independent of concentration
  • Collision theoryTerm
    Reactions need collisions with enough energy and proper orientation
  • Activation energyTerm
    Minimum energy for a successful collision
  • CatalystTerm
    Speeds a reaction by giving a lower-energy path; not consumed
  • Rate-determining stepTerm
    The slowest step in a mechanism
  • Reaction intermediateTerm
    A species made then used up within a mechanism
  • Arrhenius equationTerm
    Relates rate constant to temperature and activation energy
  • EndothermicTerm
    Absorbs heat; positive delta H
  • ExothermicTerm
    Releases heat; negative delta H
  • Specific heatTerm
    Energy needed to raise 1 g of a substance by 1 degree C
  • CalorimetryTerm
    Measuring heat flow, q = mc delta T
  • Enthalpy of formationTerm
    Heat change when 1 mol forms from elements in standard states
  • Hess's lawTerm
    Total enthalpy change is the sum of steps
  • Bond enthalpyTerm
    Energy needed to break a bond
  • EntropyTerm
    A measure of disorder or energy dispersal
  • Gibbs free energyTerm
    Delta G = delta H - T delta S; negative means spontaneous
  • Standard stateTerm
    Reference conditions for thermodynamic data, 1 bar
  • EquilibriumTerm
    Forward and reverse rates are equal
  • Equilibrium constant KTerm
    Ratio of products to reactants at equilibrium
  • Reaction quotient QTerm
    Same ratio at any moment; compare with K to predict direction
  • Le Chatelier's principleTerm
    A system at equilibrium shifts to counteract a stress
  • KspTerm
    Solubility product constant for a slightly soluble salt
  • Common ion effectTerm
    A shared ion lowers solubility
  • Arrhenius acidTerm
    Produces H+ in water
  • Bronsted-Lowry acidTerm
    A proton donor
  • Lewis acidTerm
    An electron pair acceptor
  • Conjugate acid-base pairTerm
    Two species differing by one proton
  • pHTerm
    Negative log of hydrogen ion concentration
  • KwTerm
    Ion product of water, 1.0 x 10^-14 at 25 degrees C
  • Strong acidTerm
    Dissociates completely in water
  • BufferTerm
    A solution that resists pH change; weak acid plus its conjugate base
  • Henderson-Hasselbalch equationTerm
    pH = pKa + log([A-]/[HA])
  • Titration equivalence pointTerm
    Moles of acid equal moles of base
  • IndicatorTerm
    A dye that changes color near the endpoint
  • Electrochemical cellTerm
    Converts chemical energy to electrical energy or the reverse

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