chemical energetics

Enthalpy change of formation

Enthalpy change when one mole of compound is formed from its elements under standard conditions

C(s) + O2(g) → CO2(g)

Enthalpy change of combustion

Enthalpy change when one mole of compound is completely burnt in excess oxygen under standard conditions

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

Enthalpy change of atomisation

Enthalpy change when one mole of gaseous atoms is formed from its elements under standard conditions

1-2H2(g) → H(g)

Enthalpy change of hydration

Enthalpy change when one mole of gaseous ions dissolves in water under standard conditions

Na+(aq) + aq → NaOH(aq)

Enthalpy change of solution

Enthalpy change when one mole of ionic solid dissolves in water under standard conditions

KCl(s) + aq → K+(aq) + Cl-(aq)

Enthalpy change of neutralisation

Enthalpy change when one mole of water is formed from an acid and base under standard conditions

H+ + OH- → H2O

Enthalpy change of precipitation

Enthalpy change when one mole of precipitate is formed from their ions in aqueous solution under standard conditions

Ag+(aq) + Cl-(aq) → AgCl(s)

First ionization energy

Energy required to remove an electron from each atom in one mole of gaseous atom to form one mole of gaseous cation

X+(g) + e- → X(g)

Second ionization energy

Energy reqiored to remove one electron from each atom in one mole of gaseous 1+ cation to one mole of gaseous 2+ cation

X2+(g) + e- → X+(g)

First electron affinity

Energy released when one mole of electrons is added to each atom in one mole of the atoms of the element to form one mole of gaseous 1- ions

X(g) + e- → X-(g)

Second electron affinity

Energy released when one mole of electrons is added to each gaseous 1- anion to form one mole of gaseous 2- anion

O-(g) + e- → O2-(g)

Lattice energy

Enthalpy change when one mole of crystallized solid is formed from its seperate gaseous ions under standard conditions

K+(g) + Cl-(g) → KCl(s)