AP Chemistry flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Photon energy equation

The energy of one photon is E equals h nu, or E equals h c divided by lambda, where h is Planck's constant and nu is frequency.

de Broglie wavelength

A particle with mass m and speed v has wavelength lambda equals h divided by m v, showing that matter has wave properties most noticeable for small masses.

Pauli exclusion principle

No two electrons in the same atom can have the same set of all four quantum numbers, so an orbital holds at most two electrons with opposite spins.

Average atomic mass

The weighted average mass of an element's atoms equals the sum of each isotope's fractional abundance multiplied by that isotope's atomic mass.

Formal charge formula

Formal charge equals valence electrons in the free atom minus nonbonding electrons minus half the bonding electrons assigned to that atom.

VSEPR theory

Electron domains around a central atom repel and arrange as far apart as possible, determining electron-domain geometry and, after lone pairs are considered, molecular geometry.

Hydrogen bonding requirement

Hydrogen bonding occurs when hydrogen is covalently bonded to nitrogen, oxygen, or fluorine and interacts with a lone pair on another electronegative atom.

Bond order molecular orbital

Bond order equals bonding electrons minus antibonding electrons, all divided by two; higher bond order generally means a shorter and stronger bond.

Ideal gas law

For an ideal gas, pressure times volume equals moles times the gas constant times absolute temperature; use kelvin and match units of R.

Dalton's law partial pressures

In a mixture of nonreacting gases, total pressure equals the sum of partial pressures, and each partial pressure equals its mole fraction times total pressure.

Molarity dilution equation

For dilution, the moles of solute before and after are equal, so initial molarity times initial volume equals final molarity times final volume.

Raoult's law

The vapor pressure of a volatile component above an ideal solution equals its mole fraction in the liquid multiplied by the pure component's vapor pressure.

Limiting reactant

The reactant that is completely consumed first limits the maximum amount of product formed; compare available moles divided by stoichiometric coefficients.

Net ionic equation

A net ionic equation includes only the ions and molecules that actually react, omitting spectator ions that remain unchanged in solution.

Oxidation

Oxidation is the loss of electrons by a species, accompanied by an increase in oxidation number; reduction is the gain of electrons.

Percent yield

Percent yield equals actual yield divided by theoretical yield, multiplied by one hundred, where theoretical yield comes from stoichiometry and the limiting reactant.

Rate law

A rate law expresses reaction rate as k times reactant concentrations raised to experimentally determined orders; overall order is the sum of exponents.

First-order half-life

For a first-order reaction, half-life equals the natural logarithm of two divided by the rate constant, independent of initial reactant concentration.

Arrhenius equation

The rate constant equals the frequency factor times e raised to negative activation energy divided by R times temperature, describing temperature dependence.

Rate-determining step

The slowest elementary step in a mechanism controls the overall reaction rate; intermediates in that step affect the observed rate law.

First law of thermodynamics

The change in internal energy equals heat added to the system plus work done on the system; energy is conserved in any process.

Hess's law

If a reaction is the sum of several steps, its enthalpy change equals the sum of the enthalpy changes of those steps, with step signs and coefficients adjusted.

Standard enthalpy of formation

The enthalpy change when one mole of a compound forms from its elements in standard states; standard formation enthalpy is zero for an element in its standard state.

Reaction quotient Q

Q has the equilibrium-constant form but uses current concentrations or pressures; comparing Q with K predicts whether the forward or reverse reaction is favored.

Le Chatelier's principle

When a system at equilibrium is disturbed by concentration, pressure, or temperature change, it shifts in the direction that counteracts the disturbance.

Solubility product Ksp

For a sparingly soluble salt, Ksp is the product of its constituent ion concentrations in a saturated solution, each raised to its stoichiometric coefficient.

pH definition

pH equals the negative base-ten logarithm of the hydronium ion concentration in moles per liter; at 25 degrees Celsius, pH plus pOH equals 14.

Henderson-Hasselbalch equation

For a buffer, pH equals the negative logarithm of Ka plus the logarithm of conjugate base concentration divided by weak acid concentration.

Ka and Kb relationship

For a conjugate acid-base pair in water at 25 degrees Celsius, Ka times Kb equals Kw, which is 1.0 times 10 to the negative 14.

Gibbs free energy criterion

At constant temperature and pressure, a process is spontaneous if its Gibbs free-energy change is negative, nonspontaneous if positive, and at equilibrium if zero.

Nernst equation

Cell potential equals standard cell potential minus RT divided by nF times the natural logarithm of Q; at 25 degrees Celsius use 0.0592 divided by n.

Faraday electron moles

The moles of electrons transferred in electrolysis equal current in amperes times time in seconds divided by Faraday's constant, 96485 coulombs per mole.