Chem Energetics

Front 1

formation

(ΔHf)

Back 1

Energy released or absorbed when one mole of a substance is formed from its constituent elements in their standard states under standard conditions of 1 bar and 298K.

Front 2

atomization

(ΔHatm)

Back 2

Energy absorbed when one mole of gaseous atom is formed from its elements in the standard state under standard conditions of 1 bar and 298K.

Front 3

bond dissociation energy (B.D.E.)

Back 3

Energy required to break one mole of covalent bonds between two atoms in gaseous molecule to give gaseous atoms.

Front 4

First electron affinity (1st E.A.)

Back 4

Energy released when one mole of the gaseous atoms accepts electron to form gaseous singly charged negative ions

Front 5

First ionization energy

(1st I.E.)

Back 5

Minimum energy required to remove the most loosely held electron from one mole of gaseous atoms to form gaseous singly charged ions.

Front 6

lattice energy (L.E.)

Back 6

Energy released when one mole of ionic solid is formed from its isolated gaseous ions.

Front 7

hydration

(ΔHhyd)

Back 7

Energy released when one mole of gaseous ions is hydrated into aqueous ions under standard conditions of 1 bar and 298K. |ΔHhyd| ∝ charge density of ion

Front 8

solution

(ΔHsoln)

Back 8

Energy released or absorbed when one mole of an ionic solid is dissolved in water to form a dilute solution under standard conditions of 1 bar and 298K.

Front 9

combustion

(ΔHc)

Back 9

Energy released when one mole of a substance is completely burnt in excess oxygen under standard conditions of 1 bar and 298K.

Front 10

neutralization

(ΔHn)

Back 10

Energy released when one mole of H2O is formed from the reaction between an acid and a base under standard conditions of 1 bar and 298K.

* ΔHnө of reaction involving weak acid or weak base will be less exothermic than strong acid + strong base.

e.g. ΔHnө = 57 kJmol1 for strong acid + strong base

ΔHnө < 57 kJmol1 for neutralization reactions involving weak acids OR weak bases