Chemistry EA

Dynamic Equilibrium

In a closed system, the state where forward and reverse reaction rates are equal, so concentrations of reactants and products stay constant over time

Le Châtelier's Principle

If a system at equilibrium is disturbed (temperature, concentration, pressure), it shifts to partially counteract the change

Equilibrium constant (Kc)

Ratio of product concentrations to reactant concentrations (each raised to its coefficient) at equilibrium: Kc = [C]^c[D]^d / [A]^a[B]^b

Reaction quotient (Q)

Same expression as Kc but calculated at any point in time; comparing Q to Kc predicts which way a reaction will shift

Solubility product (Ksp)

A measure of how much an ionic compound dissolves, based on ion concentrations in a saturated solution

Brønsted-Lowry acid/base

An acid donates a proton (H⁺); a base accepts a proton

Amphiprotic species

A species that can act as either a Brønsted-Lowry acid or base (e.g. water, HCO₃⁻)

Buffer solution

A solution that resists changes in pH when small amounts of acid or base are added

Ka (acid dissociation constant)

The equilibrium constant for a weak acid's ionisation, indicating its strength

Kw (ion product of water)

The equilibrium constant for water's self-ionisation: Kw = [H⁺][OH⁻]

Equivalence point vs end point

Equivalence point is where moles of acid and base are stoichiometrically equal; end point is where the indicator visibly changes colour (ideally very close to the equivalence point)

Oxidation vs reduction

Oxidation is loss of electrons; reduction is gain of electrons ("OIL RIG")

Galvanic Cell

Uses a spontaneous redox reaction to generate electrical potential difference

Electrolytic Cell

Uses an external electrical potential difference to drive a non-spontaneous redox reaction

Anode vs Cathode

Anode is the electrode where oxidation occurs; cathode is where reduction occurs

Standard electrode potential (E°)

A measure of a half-cell's tendency to be reduced, compared against the standard hydrogen electrode

Functional Group

The atom or group of atoms in an organic molecule responsible for its characteristic chemical reactions

Homologous Series

A family of compounds with the same functional group and general formula, differing by CH₂ units, with a gradual trend in physical properties

Isomers (structural vs stereo)

Structural isomers share a molecular formula but differ in structural arrangement; stereoisomers share a structural formula but differ in spatial arrangement (e.g. cis/trans, optical)

Esterification

A reversible reaction between a carboxylic acid and an alcohol to form an ester (and water)

Markovnikov's Rule

In addition of HX or water to an alkene, H attaches to the carbon already bonded to more hydrogens, forming the more stable carbocation intermediate

Zwitterion

A molecule (like an amino acid) with both a positive and negative charge on different parts, giving an overall neutral charge

Condensation Polymer

A polymer formed when monomers join with the loss of a small molecule (e.g. water), such as polyester, nylon, or proteins

Atom Economy

A measure of how much of the reactant mass ends up in the desired product, used to assess how "green" a process is

Retention Factor (Rf)

In chromatography, the ratio of the distance moved by a substance to the distance moved by the solvent