chem definitions

What is enthalpy change of vaporisation

The enthalpy change when 1 mole of a substance changes from liquid to gas at its boiling point

standard enthalpy change of combustion

The enthalpy change that occurs when 1 mole of substance completely combusts

average bond enthalpy

breaking of 1 mole of bonds in gaseous molecules

enthalpy change of hydration

the enthalpy change when 1 mole of gaseous ions dissolves in water

Enthalpy of formation

enthalpy change when 1 mole of a compound is formed from its substituent elements in standard conditions

homolytic fission

splitting of a bond to form 2 radicals

heterolytic fission

splitting of a bond to form 2 oppositely charged ions

nucleophile

electron pair donor

electrophile

electron pair acceptor

bronsted-lowry acid

proton donor

bronsted-lowry base

proton acceptor

buffer solution

a solution that minimises pH changes on addition of small amounts of acid or base

equivalence point

point in a titration when the amount of acid is equal to the amount of base

enthalpy change of solution

enthalpy change when 1 mole of an ionic compound dissolves in water

First Ionisation Energy

the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ion

standard electrode potential

the e.m.f of a half cell compared to the standard hydrogen half cell under standard conditions (1 moldm-3, 100KPa, 298K)

bidentate ligand

• species that has 2 lone pairs that can be donated to form 2 coordinate bonds with the central metal ion

Transition Elements

element that can form 1 or more ions with incomplete d-sub shells

lattice enthalpy

the enthalpy change when 1 mole of a solid ionic lattice is formed from its gaseous ions

First Electron Affinity

the enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms, forming 1 mole of gaseous 1- ions

Enthalpy Change of Atomisation (ΔH):

enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state

entropy (S)

a measure of the dispersal and disorder of energy in a system