Standary Enthalpy Changes

Standard Enthalpy change of REACTION

ΔHr⦵ , the energy change when the molar quantities of reactants as stated in the balanced equation react under standard conditions and all reactants and products are in their standard states.

Standard Enthalpy change of NEUTRALISATION

ΔHn⦵ , the enthalpy change when one mole of water is formed from an acid and alkali under standard conditions and all reactants and products are in their standard states.

Standard Enthalpy change of COMBUSTION

ΔHc⦵ , the enthalpy change when one mole of the substance burns completely in oxygen under standard conditions and all reactants and products are in their standard states.

Standard Enthalpy change of FORMATION

ΔHf⦵ , the enthalpy change when one mole of the compound forms from its elements under standard conditions and all reactants and products are in their standard states.

What are the standard conditions?

Pressure 100kPa

Temperature 298K

Substances are in their standard states (most stable form)

Solutions have a concentration of 1mol dm^-3

what is the ΔHf⦵ of an element by definition?

0kJ/mol