CLEP Chemistry flashcards
CLEP Chemistry · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Isotopes
- Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers but identical chemical behavior in most reactions.
- Aufbau principle
- Electrons fill atomic orbitals in order of increasing energy, starting with 1s and proceeding through 2s, 2p, 3s, 3p, 4s, and so on.
- Electronegativity
- The relative ability of an atom in a bond to attract shared electrons; it increases across a period and decreases down a group.
- Formal charge
- The charge assigned to an atom in a Lewis structure, calculated as valence electrons minus nonbonding electrons minus half the bonding electrons.
- VSEPR theory
- Electron domains around a central atom repel each other and spread out to maximize separation, determining molecular geometry from the number of domains.
- Ideal gas law
- The relationship PV = nRT linking pressure, volume, moles, and absolute temperature, where R is the universal gas constant.
- Dalton's law
- The total pressure of a gas mixture equals the sum of the partial pressures each gas would exert if it occupied the volume alone.
- Graham's law
- The effusion rate of a gas is inversely proportional to the square root of its molar mass, so lighter gases effuse more rapidly.
- Sublimation
- A phase transition in which a solid converts directly to a gas without passing through the liquid state, absorbing heat in the process.
- Combustion reaction
- A reaction in which a substance reacts with oxygen, releasing energy; hydrocarbons yield carbon dioxide and water when oxygen is sufficient.
- Precipitation reaction
- A double replacement reaction in which two soluble salts form an insoluble solid product that separates from the solution.
- Oxidation number
- A bookkeeping value assigned to an atom in a compound used to track electron transfer; an increase indicates oxidation and a decrease indicates reduction.
- Activity series
- A ranking of metals by their tendency to lose electrons; a metal displaces ions of any metal ranked below it in single replacement reactions.
- Limiting reactant
- The reactant that is completely consumed first in a reaction, determining the maximum amount of product that can be formed.
- Percent yield
- The actual mass of product obtained divided by the theoretical mass predicted from stoichiometry, multiplied by one hundred.
- Molarity
- A concentration unit equal to the number of moles of solute dissolved per liter of solution, abbreviated M.
- Empirical formula
- The simplest whole-number ratio of atoms of each element in a compound, derived from percent composition by mass.
- Le Châtelier's principle
- When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, it shifts to partially offset that change.
- Reaction quotient Q
- The product-over-reactant ratio computed with current concentrations; comparing Q with K predicts the direction of net reaction.
- pH
- The negative base-ten logarithm of the hydrogen ion concentration, indicating acidity on a scale typically from zero to fourteen.
- Kw
- The ion product of water, equal to the product of hydrogen and hydroxide ion concentrations, which is 1.0×10^−14 at 25 °C.
- Rate law
- An equation relating reaction rate to reactant concentrations raised to experimentally determined powers, with a temperature-dependent rate constant.
- Activation energy
- The minimum energy that colliding particles must possess for a reaction to occur, lowered by a catalyst and reflected in the Arrhenius equation.
- Catalyst
- A substance that increases reaction rate by providing an alternative pathway with lower activation energy without being consumed overall.
- First-order half-life
- For a first-order reaction, the time required for reactant concentration to fall to half its value, equal to 0.693 divided by the rate constant.
- Hess's law
- The enthalpy change of an overall reaction is the sum of the enthalpy changes of its steps, regardless of the pathway taken.
- Gibbs free energy
- A thermodynamic quantity given by ΔG = ΔH − TΔS; a negative value indicates a spontaneous process at constant temperature and pressure.
- Enthalpy of formation
- The enthalpy change when one mole of a compound forms from its elements in their standard states; elements in standard states have zero value.
- Calorimetry
- An experimental method measuring heat exchanged during a process, commonly using q = mcΔT with a known specific heat capacity.
- Strong acid
- An acid that ionizes essentially completely in water, such as hydrochloric, nitric, or sulfuric acid, producing high hydrogen ion concentration.
- Amphoteric substance
- A substance that can act as either a Brønsted acid or a base, donating or accepting a proton depending on the other reactant present.
- Titration
- A procedure in which a solution of known concentration is added to a measured volume of unknown until the equivalence point is reached.