Chem- A2 Inorganic & Physical definitions Flashcards
Redox
A reaction in which both oxidation and reduction take place
Oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of a different element
Oxidising agent
A reagent that oxidises (takes electrons from) another species
Reducing agent
A reagent that reduces (adds electrons to) another species
Standard electrode potential
The e.m.f of a half cell compared with a standard hydrogen half cell, measured at 298K with all solution concentrations of 1 mol dm^-3 and a gas pressure of 100kPa (1 atm)
Fuel cell
Uses the energy from the reaction of a fuel with oxygen to create a voltage
d-block elements
The highest energy sub-shell is a d sub-shell
Transition elements
d block elements that have an ion with an incomplete d sub-shell
Ligand
A molecule or ion that can donate a pair of electrons to a transition metal ion to form a coordinate bond
Complex ion
A transition metal ion bonded to one or more ligands by coordinate bonds
Coordinate bond
A shared pair of electrons in which one of the bonded atoms provides both the electrons for the shared pair
Coordination number
The total number of coordinate bonds formed between a central metal ion and its ligands
Bidentate ligand
A ligand which can donate two lone pairs of electrons to a metal ion from two separate atoms to form two coordinate bonds
Ligand substitution
A reaction in which one ligand in a complex ion is replaced by another ligand
Stereoisomers
Species with the same structural formula but with different arrangements of atoms in space
Optical isomers
Stereoisomers that are a pair of non-superimposable mirror images of each other
le Chatelier’s
When a system in dynamic equilibrium is subjected to change, the equilibrium position will shift to minimise the change
Acid
proton donor
Base
proton acceptor
Conjugate acid-base pairs
A pair of two species that transform into each other by gain or loss of a proton
Strong acid
A proton donor that completely dissociates in solution
Weak acid
A proton donor that partially dissociates in solution
Acid dissociation constant
Shows the extent of acid dissociation and is defined as: Ka= ([H+][A-]) ÷ [HA]
for acid HA: HA(aq) <=> H+(aq) + A-(aq)
pH
pH= -log[H+]
Ionic product of water, Kw
Kw= [H+][OH-] (at 25C, Kw= 1.00x10^-14 mol^2 dm^-6)
Buffer solution
A system that minimises pH changes on addition of small amounts of an acid or a base
Lattice enthalpy
The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions
Enthalpy change of solution
The enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions
Enthalpy change of hydration
The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions
Enthalpy change of formation
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states, under standard conditions
First ionisation energy
The enthalpy change accompanying the removal of one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
Second ionisation energy
The enthalpy change accompanying the removal of one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
Enthalpy change of atomisation
The enthalpy change that takes place when one mole of gaseous atoms forms from the element in its standard state
First electron affinity
The enthalpy change accompanying the addition of one electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions
Second electron affinity
The enthalpy change accompanying the addition of one electron to each ion in one mole of gaseous 1- ions to form one mole of gaseous 2- ions
Entropy, S
The quantitative measure of the degree of ‘disorder’ in a system
Free energy change, ΔG
The balance between entropy, enthalpy, and temperature for a process: ΔG= ΔH -TΔS
A process can take place spontaneously when ΔG<0 (when ΔG is negative)
Rate of reaction
The change in concentration of a reaactant or product per unit time
Order, m
The order with respect to a reactant is the power to which the concentration of the reactant is raised in the rate equation
Rate constant, k
The constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation
Rate equation (general)
for A +B -> products: rate= k[A]^m [B]^n
Half-life
The time taken for the concentration of a reactant to be reduced by half
Rate determining step
The slowest step in the reaction mechanism of a multi-step reaction
