A2 2 Definitions Flashcards
Standard Enthalpy of formation
The Enthalpy change when 1 mole of a substance is formed from its elements, in their natural state, under standard conditions
Standard Enthalpy of atomisation
The Enthalpy change when 1 mole of gaseous atoms is formed from its elements in its standard state
1st ionisation energy
The energy required to remove 1 electron from each atom in one mole of gaseous atoms, to form one mole of gaseous 1+ ions
2nd ionisation energy
The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
1st electron affinity
The energy required to form one mole of negatively charged ions from one mole of atoms, in the gaseous state
2nd electron affinity
The energy required to form 1 mole of 2- ions from one mole of 1- ions, in the gaseous state
Hess’ Law
The Enthalpy change for a reaction is the same,irrespective of the route taken, provided the initial and final conditions are the same
Standard Enthalpy of solution
Enthalpy change when one mole of a compound is completely dissolved in water, under standard conditions
Standard Enthalpy 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
Entropy
A measure of disorder in a system (S)
Standard electrode potential
The voltage of a half cell, compared to a standard hydrogen half cell, measured at 298K, with solution concentrations of 1moldm-3 and a gas pressure of 1atm
Standard Lattice Enthalpy
The Enthalpy change when one mole of a solid ionic lattice is formed, from its gaseous ions under standard conditions. Always exothermic
Transition element
A d block element, that forms an ion with an incomplete d sub shell
Catalyst
Increases the rate of reaction, without being used up. Provides an alternative route, with lower activation energy
Ligand
A molecule or ion which possesses at least one lone pair of electrons, which can be donated into vacant d orbitals of a metal ion, by forming a co-ordinate bond
Co-ordination number
The total number of co-ordinate bonds formed between a central metal ion and it’s ligands
Bidentate ligand
Can donate two lone pairs of electrons into the vacant d orbitals of a metal ion, forming two co-ordinate bonds
Dynamic equilibrium
Reached in a closed system where:
- rate of forward reaction equals the rate of the reverse reaction
- the concentrations of the reactants and products remain the same but are constantly interchanging
Le Chatelier’s principle
When a system in equilibrium is subjected to a change, the position of equilibrium will shift to minimise that change
Bronstead Lowry theory
Acid: proton donor
Base: proton acceptor
Buffer
Minimises changes in pH, on addition of small amounts of acid or base
Titration end point
The stage where the indicator used has a colour halfway between it’s extreme colours
Equivalence point
The point of neutralisation - when an acid and a base have completely reacted
Standard Enthalpy change of Neutralisation
The energy change when an aqueous acid is neutralised by an aqueous base, to form one mole of water, under standard conditions
Oxidation state
State which a metal achieves as a result of losing electrons
Precipitation reaction
A reaction in which soluble ions, in separate solutions, are mixed together to produce an insoluble compound or precipitate
Order
The power to which the concentration of a reactant is raised in the rate equation
Rate determining step
The slowest step in the reaction mechanism of a multi step reaction
Rate
Change in concentration of a reactant or product with time
Initial Rate
The rate at the start of a reaction, when t=0
