A2 Chemistry

Lattice energy is the enthalpy change when 1 mole of an ionic solid is formed from its gaseous ions under standard conditions.

The enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state under standard conditions.

The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

The enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1− ions.

A measure of the disorder or randomness of a system. The greater the disorder, the higher the entropy.

The energy associated with a chemical reaction that can be used to do work. It is given by the equation: ΔG = ΔH − TΔS.

The potential difference between a half-cell and the standard hydrogen electrode under standard conditions (298 K, 1 atm, and 1 mol dm⁻³ concentration).

The Nernst equation relates the reduction potential of an electrochemical cell to the standard electrode potential, temperature, and the activities (or concentrations) of the chemical species involved. E = E° − RT/nF ln Q.

A reference electrode based on the half-cell: 2H⁺(aq) + 2e⁻ → H₂(g), with a standard electrode potential of 0.00 V.

The ratio of the concentrations of products to reactants, each raised to the power of their stoichiometric coefficients at equilibrium.

The pressure exerted by a single gas in a mixture of gases, proportional to its mole fraction in the mixture.

The equilibrium constant for a reaction involving gases, expressed in terms of the partial pressures of the reactants and products.

If a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will shift to counteract that change and restore a new equilibrium.

A d-block element that forms at least one stable ion with a partially filled d-subshell.

A molecule or ion that donates a lone pair of electrons to a central metal ion to form a coordinate (dative covalent) bond.

The number of coordinate bonds formed between the central metal ion and ligands in a complex ion.

A charged species consisting of a central metal ion bonded to one or more ligands by coordinate bonds.

A ligand that can form two coordinate bonds with a central metal ion.

A substance that increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy, without being consumed in the process.

The enthalpy change when one mole of gaseous atoms each gains an electron to form one mole of gaseous 1− ions.

The measure of the size of an ion, typically based on the distance between nuclei of adjacent ions in a crystal lattice.

A functional group consisting of a carbon atom double-bonded to an oxygen atom (C=O).

A reaction where a nucleophile donates a pair of electrons to a carbonyl carbon, leading to the addition of the nucleophile to the carbon.

A chemical reaction between a carboxylic acid and an alcohol to form an ester and water, typically catalyzed by an acid.

The chemical breakdown of a compound due to reaction with water. For esters, hydrolysis results in the formation of a carboxylic acid and an alcohol (or carboxylate salt in alkaline conditions).

A carboxylic acid derivative where the hydroxyl group (-OH) is replaced by a chlorine atom (-Cl).

A compound that contains a benzene ring (C₆H₆) or another ring system with delocalized π-electrons above and below the plane of the ring.

A reaction where an electrophile replaces a hydrogen atom in an aromatic ring.

An organic compound derived from ammonia, where one or more hydrogen atoms are replaced by alkyl or aryl groups.

A molecule containing both an amine group (-NH₂) and a carboxylic acid group (-COOH). Amino acids are the building blocks of proteins.

A polymerization reaction in which unsaturated monomers (e.g., alkenes) join together without the loss of any atoms to form a polymer.

A polymerization reaction where monomers join together with the loss of small molecules, such as water or hydrogen chloride, to form a polymer.

A technique used to identify chemical compounds by measuring the absorption of infrared radiation, which causes molecular vibrations at specific frequencies.

The ion formed when a molecule loses an electron during mass spectrometry, representing the entire molecule with a positive charge.

The position of an NMR absorption signal, measured in parts per million (ppm), which indicates the environment of the nucleus being analyzed.

The interaction between neighboring non-equivalent nuclei, causing splitting of NMR signals into multiplets.