Definitions Flashcards
Lewis acid
Electron pair acceptor
Amphoteric
An amphoteric oxide is one which is capable of reacting with both acids and bases- eg aluminium oxide
Lewis base
Electron pair donor
Standard electromotive force
The potential difference between the electrodes of a standard electrochemical cell measured under zero conditions
Primary cell
Irreversible cell and is not intended to be recharged by electric current
Secondary cell
Reversible and rechargeable
Fuel cell
Generates electricity from continuous oxidation or an external source of fuel
Delta H
The standard enthalpy change at 298k
Electron affinity
Standard molar enthalpy change for the addition of an electron to an isolated atom in the gas phase
Enthalpy change
Amount if heat energy released or absorbed when a chemical/ physical change occurs at constant pressure
Enthalpy of atomisation
Standard enthalpy change for the formation of one mole of gaseous atoms from the element in its standard state
Enthalpy of fusion
Enthalpy change then a solid forms a liquid at its melting point
Enthalpy of hydration
Enthalpy change for the formation. Of aqueous ions from gaseous ions
Lattice enthalpy of formation
Enthalpy change for the formation of a solid ionic lattice from its gaseous atoms
Lattice enthalpy of dissociation
Enthalpy change for the separation of a solid ionic lattice into its gaseous ions
Enthalpy of solution
Enthalpy change that occurs when an ionic solid dissolves in enough water that the ions are well separated and do not interact with one another
Enthalpy of sublimation
Enthalpy change that occurs on sublimation, when a solid changes directly to a gas without forming liquid phase
Enthalpy of vaporisation
The standard molar enthalpy change when a liquid forms a gas at its boiling point
Entropy
A measure of disorder of a system
First ionisation enthalpy
Enthalpy change for the removal of an electron from an atom in the gas phase to form a positive ion and an election in the gaseous phase.
Electrochemical series
A list of standard electrode potentials arranged in order of their numerical values
Adsorption
The process by which a substance is weakly bonded to and held in place on a solid surface.
Acidity reaction
A reaction of a metal aqua ion in which an 0-H bond in a co-ordinated water molecule is broken, releasing H+ ions.
Aqua ion
A metal surrounded by water Ligands
Beer-Lambert law
A=ecl where absorbance A, concentration C, cell-path-length L, and molar absorbance coefficient e, are linked
A change in colour in a complex can arise from….
Change in co-ordination number, ligand or oxidation state.
Chelate effect
The effect of driving a reaction in the forward direction when a bidentate or multidentate reacts with a compound surrounded by unidentate Ligands.
Combined heat and power systems
Domestic electricity generation systems which use up waste heat to provide local heating- these systems are more cost efficient by feeding excess electrical power backwards- into the grid
Feasible change
One which has a natural tendency to occur without being driven my external influences
Free radical
A species which results from homolytic fission, containing an unpaired electron
Fuel cell
One in which produces electrical power from an external supply of a fuel and an oxidant
Gas electrode
An inert metal surrounded by gas in equilibrium with a solution of its ions
Ground state
The lowest energy state of electrons in a species
Haemoglobin
A octahedrally co-ordinated iron2 complex, responsible for the red pigment in red blood cells and transporting oxygen in the blood
Heterolytic fission
Formation of ions when a covalent bond breaks with an unequal splitting of the bonding pair of electrons
Homolytic fission
Formation of radicals when a covalent bond breaks with an equal splitting of the bonding pair of electrons
Inert support medium
An I reactive solid used to dilute a reagent or a catalyst
Mixed catalyst
Those prepared by mixing two or more catalytic substances
Non rechargeable cell
One not intended to be recharged by an electric current- also known as a primary cell
Nucleophile
Electron pair donor
Oxidation state
The charge a central metal atom in a complex would have if it existed as a solitary simple ion without bonds to other species
Planck’s constant
The constant of proportionality between energy (delta E) of absorbed light and it’s frequency. Delta E=hv
Salt bridge
An electrolyte solution used to complete electrical contact between two electrode compartments- allows the transfer of ions between compartments
Sequestering ability
The peppery of a substance to keep metal ions in solution even when anions which normally cause precipitation are added
Titrations using potassium dichromate
When using an oxidising agent in acidic solution there is no distinctive colour change at the end-point, and indicator is needed- sodium diphenlyaminesulfonate- colourless to pink
Visible spectrophotometer
A device that uses visible light of varying frequencies to measure the amount of light absorbed by a coloured solution. Absorption is proportional to the concentration of absorbing species under test
