IB Chemistry

An absorption spectrum shows dark lines against a continuous background.

The equilibrium constant for the dissociation of a weak acid in water, $K_a = \mathrm{\frac{[H^+][A^-]}{[HA]}}$. A larger value of $K_a$ means the acid dissociates more fully, so it is a stronger acid.

Acid–base indicators are weak acids that exist in equilibrium between their protonated form (HInd) and deprotonated form (Ind⁻).

The activated complex is a high-energy, unstable arrangement of atoms that exists momentarily as reactants are transformed into products. It represents the "peak"; of the energy barrier in a reaction.

Activation energy ($E_a$) is the minimum energy required for colliding particles to form an activated complex (also known as the transition state) and proceed to products.

Addition polymerization is a reaction in which monomers with double or triple bonds join together without forming any by-products, creating a polymer chain.

One of two or more different structural forms of the same element in the same physical state. Diamond, graphite, graphene, and fullerenes are all allotropes of carbon.

An alloy is a mixture of a metal with one or more other elements, which can be either metals or non-metals

An amphiprotic species is a chemical species that can either donate a proton (acting as an acid) or accept a proton (acting as a base), depending on the reaction conditions.

An anion is formed when an atom gains one or more electrons, resulting in a net negative charge.

The anode is the electrode in an electrochemical cell where oxidation occurs. Electrons are produced at the anode and flow into the external circuit.

The positively charged, non-aromatic intermediate formed when a benzene ring donates a pair of π-electrons to an electrophile. Its delocalized system is broken, so it is less stable than benzene.

An equation relating the rate constant $k$ to temperature: $k = Ae^{-\frac{E_a}{RT}}$, where $A$ is the Arrhenius factor, $E_a$ is the activation energy, $R$ is the gas constant, and $T$ is the absolute temperature in kelvin.

The pre-exponential constant $A$ in the Arrhenius equation ($k = Ae^{-E_a/RT}$). It represents the frequency of correctly oriented collisions between reactant particles and has the same units as the rate constant $k$.

Atom economy is a measure of how efficiently the atoms in the reactants are used to form the desired product in a chemical reaction.

Atom economy measures how efficiently the atoms in the reactants are incorporated into the desired product.

The atomic radius is the distance from the nucleus of an atom to the outermost electron.

Average bond enthalpy represents the average energy required to break a given bond across a range of compounds.

Avogadro's law states that equal volumes of all gases, measured under the same conditions of temperature and pressure, contain equal numbers of molecules.

Biofuels are energy sources derived from biological materials such as plants, algae, or organic waste.

The energy required to break one mole of a specific bond in the gaseous state is called its bond enthalpy (or bond dissociation energy)

Bond length is the average distance between the nuclei of two bonded atoms.

Bond polarity refers to the unequal sharing of electrons between two atoms in a covalent bond, resulting in a partial positive charge on one atom and a partial negative charge on the other.

Bond strength refers to the energy required to break a bond.