Chemical Energetics: Components of energy level diagram

Standard enthalpy of combustion

Energy released when one mole of compound is completely burnt in O2 under s.t.p of 298k and 1 bar

Eqn for standard enthalpy of combustion

S2 (s) + O2(g) → SO2 (g)

Standard enthalpy change of neutralization

Enthalpy change when one mole of H2O is formed from the neutralization of an acid & alkali in aqueous solution under s.t.p of 298k and 1 bar

Eqn for standard enthalpy change of neutralization

(normal acid base reaction → salt + H2O)

Bond energy (of dissociation)

Energy required to break one mole of a covalent bond between two atoms in the gaseous state

Eqn for Bond energy

AB → A(g) + B(g)

Standard enthalpy change of formation

Enthalpy change when one mole of a compound is formed from its elements at s.t.p of 298k and 1 bar.

Eqn of enthalpy change of formation

H2 (g) + ½ O2 → H2O (l)

Standard enthalpy change of hydration

Enthalpy change when one mole of gaseous ions is dissolved in a large volume of water that the addition of more water would lead to no further heat change.

Eqn for enthalpy change of hydration

Na+ (g) + aq → Na+ (aq)

Enthalpy change of solution

One mole of substance is dissolved in such a large volume of solvent that the addition of more solvent would lead to no further hear change.

Eqn for enthalpy change of hydration

NaCl (s) + aq → Na+ (aq) + Cl- (aq)

NH3 (g) + aq → NH3 (aq)

Lattice Energy

Energy evolved when one mole of ionic solid is evolved from its separate gaseous ions

Eqn for lattice energy

K+(g) + Cl-(g) → KCl(s)

Enthalpy change of atomization

One mole of separate gaseous atoms are formed from its element under s.t.p of 298k and 1 bar.

Eqn for enthalpy change of atomization

Na (s) → Na (g)

Ionization energy

Energy required to remove one mole of electrons from one mole of gaseous atoms or ions to produce one mole of gaseous cations.

Eqn for ionization energy

X(g) → X+(g) + e-

X+(g) → X2+ (g) + e-

Electron affinity

Energy change when one mole of electrons is added to one mole of gases atoms to produce one mole of gaseous anions.

Eqn for electron affinity

Cl (g) + e- → Cl- (g)