OAE Chemistry flashcards
OAE 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.
- Hypothesis
- A testable, falsifiable prediction about the relationship between variables, based on prior observations and used to guide experimental design.
- Independent variable
- The factor deliberately changed or manipulated by the experimenter to observe its effect on the dependent variable.
- Accuracy vs precision
- Accuracy is closeness to the true value; precision is reproducibility among repeated measurements. Random errors reduce precision; systematic errors reduce accuracy.
- Significant figures
- Digits in a measurement that carry meaning about precision. Nonzero digits and zeros between them count; leading zeros do not; trailing zeros after a decimal count.
- Dimensional analysis
- A problem-solving method using conversion factors so that unwanted units cancel, leaving the desired unit; e.g., 1 in = 2.54 cm.
- Scientific theory
- A well-substantiated explanation of some aspect of the natural world, supported by repeated evidence and subject to revision with new data.
- Isotope
- Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers.
- Average atomic mass
- The weighted average of the masses of all naturally occurring isotopes of an element, calculated using their fractional abundances.
- Bohr model
- A model in which electrons occupy quantized energy levels around the nucleus; transitions between levels absorb or emit photons of specific energy.
- Aufbau principle
- Electrons fill atomic orbitals in order of increasing energy, starting with the lowest-energy orbital, to determine electron configurations.
- Periodic trend: atomic radius
- Atomic radius decreases across a period because effective nuclear charge increases, and increases down a group because additional electron shells are added.
- Mole
- The amount of substance containing 6.022×10^23 representative particles (Avogadro's number); its mass in grams equals the molar mass.
- Ionic bond
- An electrostatic attraction between oppositely charged ions formed by the transfer of electrons, typically between a metal and a nonmetal.
- Covalent bond
- A bond formed by the sharing of electron pairs between atoms, typically between nonmetals, creating molecules.
- VSEPR theory
- Valence Shell Electron Pair Repulsion theory predicts molecular shape by arranging electron domains around a central atom to minimize repulsion.
- Hybridization
- The mixing of atomic orbitals to form new hybrid orbitals that explain molecular geometry; sp, sp², and sp³ correspond to linear, trigonal planar, and tetrahedral arrangements.
- Hydrogen bonding
- A strong intermolecular force between a hydrogen atom bonded to N, O, or F and a lone pair on a nearby electronegative atom.
- Limiting reactant
- The reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product that can form.
- Percent yield
- The ratio of actual yield to theoretical yield, multiplied by 100, expressing the efficiency of a reaction.
- Mole ratio
- The ratio of coefficients from a balanced chemical equation, used to convert moles of one substance to moles of another.
- Net ionic equation
- A chemical equation showing only the species that actually participate in the reaction, omitting spectator ions that remain unchanged.
- Empirical formula
- The simplest whole-number ratio of atoms of each element in a compound, determined from percent composition or experimental data.
- Enthalpy change
- The heat absorbed or released at constant pressure during a reaction; negative ΔH indicates exothermic, positive indicates endothermic.
- Hess's law
- The overall enthalpy change of a reaction equals the sum of enthalpy changes of its individual steps, allowing indirect determination of ΔH.
- Gibbs free energy
- A thermodynamic quantity defined as ΔG = ΔH – TΔS; a negative ΔG indicates a spontaneous process at constant temperature and pressure.
- Activation energy
- The minimum energy required for colliding particles to react; catalysts lower activation energy without being consumed.
- Le Chatelier's principle
- When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, it shifts to counteract the disturbance.
- Molarity
- A concentration unit defined as moles of solute per liter of solution, abbreviated M.
- Colligative properties
- Physical properties of solutions that depend on the number of solute particles, including boiling point elevation, freezing point depression, and osmotic pressure.
- pH
- A measure of acidity defined as –log[H3O+]; pH less than 7 is acidic, 7 is neutral, and greater than 7 is basic at 25°C.
- Buffer
- A solution containing a weak acid and its conjugate base (or weak base and conjugate acid) that resists large pH changes when acid or base is added.
- Henderson–Hasselbalch equation
- pH = pKa + log([A–]/[HA]), used to calculate the pH of a buffer solution from the ratio of conjugate base to weak acid.