Enthalpy

Exothermic Delta H

negative

Endothermic Delta H

positive

Activation energy

the minimum energy required for a reaction to take place

Standard pressure

100kPa

Standard temperature (Celcius)

25

Standard concentration

1 moldm-3

standard temperature (Kelvin)

298

Standard enthalpy change of combustion

the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states

Standard enthalpy change of formation

the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states

Standard enthalpy change of reaction

the enthalpy change that accompanies a reaction in the molar quantities shown in the chemical equation under standard conditions, with all reactants and products in their standard states

Standard enthalpy change of neutralisation

the enthalpy change that accompanies a reaction of an acid and a base to form one mole of H2O under standard conditions, with all reactants and products in their standard states

Average bond enthalpy

the energy required to break one mole of a specified bond in a gaseous molecule

Hess’ Law

The enthalpy change for a reaction (under standard conditions) is independent of the route taken