• IB Chemistry Definitions

The following is a list of the definitions required for IB according to the syllabus. The intention for creating this is to have a compilation of all the definitions that one may be asked for on an exam, in a format such that a few sheets can be printed out and placed somewhere where they are viewed frequently (e.g. toilet door!). This is because they need to be learned essentially word-for-word rather than explained. Please feel free to contribute below to the essential definitions for IB chemistry. try to keep in alphabetical order. Avoid posting definitions for option topics.

Acid Lewis: substance that can accept an electron pair

           Bronsted-Lowry: substance that can donate a proton

Activation energy minimum amount of energy required to bring about a reaction

Average bond enthalpy mean enthalpy required to break a particular covalent bond in a range of molecules

Base Lewis: substance that can donate an electron pair

            Bronsted-Lowry: substance that can accept a proton. 

Electronegativity relative ability of a covalently-bonded atom to attract a bonding pair of electrons to itself.

Electron Affinity enthalpy change when one mole of gaseous atoms or anions gains electrons to form a mole of negatively charged gaseous atoms

Endothermic reaction A reaction where more energy is required to break the reactant bonds than is given out when the products are formed

Exothermic Reaction A reaction where more energy is given out than needs to be put in to break the reactant bonds.

First Ionization energy amount of energy required to remove one mole of electrons from an mole of the element in a gaseous state

Isotopes of an element atoms with same number of protons but a different number of neutrons.

lattice enthalpy energy required to convert one mole of a solid compound into gaseous ions.

Ligand species that can donate a pair of non-bonding electrons to the central ion in the complex.

oxidation the loss of one or more electrons from a substance

oxidising agent

Rate of reaction increase in the concentration of one of the products per unit of time

Reduction the gain of one or more electrons by a substance

Reducing agent

Relative atomic mass weighted mean mass of all the naturally occurring isotopes of an element relative to one twelfth of a carbon-12 atom

Relative molecular mass the sum of the relative atomic masses of the constituent atoms of a molecule.

Standard electrode potential

Standard state

Standard enthalpy change of combustion

Standard enthalpy change of formation

Standard enthalpy change of reaction enthalpy change when molar quantities of reactants in their normal states react to form products in their normal states under standard conditions (1atm, 198 K)

OPTIONS antioxidant

genetically modified food

iodine number


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