A2 CIE and HESI A2 Chemistry Review

Comprehensive practice flashcards covering vocabulary from A2 Chemistry and HESI A2 Chemistry notes, including thermodynamics, kinetics, organic chemistry, and atomic structure.

Standard enthalpy change of atomisation (\Delta H_{at}^{ ⤢ })

The enthalpy change when $1\,mole$ of gaseous atoms is formed from its element under standard conditions.

Lattice energy (\Delta H_{latt}^{ ⤢ })

The enthalpy change when $1\,mole$ of an ionic compound is formed from its gaseous ions under standard conditions.

First electron affinity (EA1)

The enthalpy change when $1\,mole$ of electrons is added to $1\,mole$ of gaseous atoms to form $1\,mole$ of gaseous $1-$ ions under standard conditions.

Standard enthalpy change of solution (\Delta H_{sol}^{ ⤢ })

The enthalpy change when $1\,mole$ of an ionic substance dissolves in sufficient water to form a very dilute solution.

Standard enthalpy change of hydration (\Delta H_{hyd}^{ ⤢ })

The enthalpy change when $1\,mole$ of a specified gaseous ion dissolves in sufficient water to form a very dilute solution.

Entropy (S)

A measure of how disordered a system is, representing the number of possible arrangements of the particles and their energy.

Gibbs free energy (G)

The energy change that takes into account both the entropy change of a reaction and the enthalpy change, defined by the equation $\Delta G^{⤢} = \Delta H_{reaction}^{⤢} - T\Delta S_{system}^{⤢}$.

Electrolysis

The breaking down of a compound into its elements using an electric current.

Anode

The positive electrode in an electrolytic cell.

Cathode

The negative electrode in an electrolytic cell.

Faraday's constant (F)

The charge on $1\,mole$ of electrons, valued at approximately $96\,500\,C\,mol^{-1}$.

Standard electrode (redox) potential (E^{⤢})

The electrode potential of a half-cell when measured with a standard hydrogen electrode as the other half-cell.

Brønsted acid

A species that can donate a proton.

Brønsted base

A species that can accept a proton.

Acidic dissociation constant (Ka)

The equilibrium constant for the dissociation of an acid, calculated as $K_{a} = \frac{[H^{+}][A^{-}]}{[HA]}$.

Ionic product of water (Kw)

The equilibrium constant for the ionisation of water, defined as $K_{w} = [H^{+}][OH^{-}]$.

Buffer solution

A solution that has the ability to resist small changes in pH upon the addition of small amounts of either acid or base.

Solubility product (Ksp)

The product of the concentrations of each ion in a saturated solution of a sparingly soluble salt at $298\,K$, raised to the power of their relative concentrations.

Partition coefficient (Kpc)

The ratio of the concentrations of a solute in two different immiscible solvents in contact with each other when equilibrium has been established.

Half-life (t1/2)

The time taken for the concentration of a limiting reactant to become half of its initial value.

Rate-determining step

The slowest step in a chemical reaction mechanism.

Homogeneous catalysis

Occurs when the catalyst is in the same phase as the reaction mixture.

Heterogeneous catalysis

Occurs when the catalyst is in a different phase to the reaction mixture, where molecules react at the surface of a solid catalyst.

Transition element

A d-block element that forms one or more stable ions with an incomplete d subshell.

Ligand

A molecule or ion with one or more lone pairs of electrons available to donate to a central transition metal ion.

Co-ordinate number

The number of co-ordinate bonds formed by ligands to the central transition metal ion in a complex.

Chemical adsorption

The process where reactant molecules become bonded to atoms on the surface of a solid catalyst.

Desorption

The process where bonds between the catalyst surface and products weaken and are eventually broken.

Optically active

Enantiomers that exist as optical isomers and rotate plane polarised light in opposite directions.

Isotopes

Different kinds of the same atom that vary in weight/mass.

Solute

The part of a solution being dissolved.

Solvent

The part of a solution in which the solute is being dissolved.

Alloys

Solid solutions of metals, such as bronze which is a mixture of copper and tin.

Amalgams

A specific type of alloy in which another metal is dissolved in mercury.

Emulsions

Mixtures of matter that readily separate, such as water and oil.

Hydrogen bonds

The strongest intermolecular forces resulting from the attraction for a hydrogen atom by a highly electronegative element like Fluorine, Oxygen, or Nitrogen.

Dispersion forces

The weakest intermolecular forces occurring when electrons concentrate on the end of an atom, causing a momentary dipole.

Oxidation

The process involving the loss of electrons.

Reduction

The process involving the gain of electrons.

Radioactivity

The emission of particles and/or energy from an unstable nucleus.

Alpha radiation

The emission of helium nuclei containing two protons and two neutrons, resulting in a charge of $+2$.

Beta radiation

High-energy, high-speed electrons that decay from neutrons or protons and have virtually no mass.

Gamma radiation

High-energy electromagnetic radiation similar to X-rays but with higher energy, requiring lead shielding for protection.

Glycolysis

The metabolism of glucose into two molecules of pyruvate to produce $2\,molecules$ of ATP.

Gluconeogenesis

The process in which the liver produces glucose from non-carbohydrate sources like proteins or fats.

Saturated fats

Fats containing no double bonds between the carbon atoms of the fatty acid chains.

Unsaturated fats

Fats containing one or more double bonds between carbon atoms in the fatty acid chains.

Stability constant (Kstab)

The equilibrium constant for the formation of a complex ion in a solvent from its constituent ions or molecules.

Common ion effect

The reduction in solubility of a dissolved salt achieved by adding a solution of a compound containing an ion in common with the salt.

Isoelectric point

The pH (e.g., $6.0$ for alanine) where an amino acid exists as a zwitterion and is equally attracted to the anode and cathode.