22.1 Lattice enthalpy

Question 1

lattice enthalpy, Δ(LE)H ⦵

Answer 1

is the enthalpy change that accompanies the formation of
one mole of an ionic compound from its gaseous ions
under standard conditions

Δ(LE)H ⦵ = gaseous ions –> ionic lattice

is a measure of the strength of ionic bonding in a giant ionic lattice

Question 2

Born - Haber cycle

Answer 2

gaseous ions

gaseous atoms

elements in standard states

ionic lattice

Question 3

route 2:

Answer 3

lattice formation from its elements in standard states = the enthalpy change of formation, ΔfH

Question 4

is ΔfH exothermic or endothermic

Answer 4

exothermic = bonds are formed

Question 5

standard enthalpy change of formation, ΔfH⦵

Answer 5

is the ΔH 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

Question 6

route 1:

Answer 6

1. formation of gaseous atoms from elements
2. formation of gaseous ions from gaseous atoms
3. lattice formation from gaseous ions (lattice enthalpy)

Question 7

formation of gaseous atoms from elements

Answer 7

enthalpy change of atomisation

Question 8

standard enthalpy change of atomisation, ΔatH⦵

Answer 8

is the ΔH that takes place for the formation of one mole of gaseous atoms from the element
in its standard state under standard conditions

Question 9

is ΔatH exothermic or endothermic

Answer 9

endothermic = bonds are broken

Question 10

formation of gaseous ions from gaseous atoms

Answer 10

first ionisation energy

Question 11

first ionisation energy Δ(IE)H⦵

Answer 11

is the ΔH required to remove one electron from each atom
in one mole of gaseous atoms
to form one mole of gaseous 1+ ions
e.g Na(g) –> Na+(g) + e-

Question 12

are ionisation energies exothermic or endothermic

Answer 12

endothermic = energy is required to overcome the attraction between a negative electron and the positive nucleus

Question 13

what is the opposite of ionisation energy

Answer 13

electron affinity
electron affinity measures the energy to gain electrons

Question 14

what measures the energy to lose electrons

Answer 14

ionisation energy

Question 15

what measures the energy to gain electrons

Answer 15

electron affinity

Question 16

first electron affinity, Δ(EA)H⦵

Answer 16

is the ΔH that takes place when one electron is added to each atom
in one mole of gaseous atoms
to form one mole of gaseous 1- ions
e.g Cl(g) + e- –> Cl-(g)

Question 17

are first electron affinities exothermic or endothermic

Answer 17

exothermic = the electron being added is attracted in towards the nucleus

Question 18

order of route 1:

Answer 18

1. ΔH of atomisations +
2. first ionisation energies +
3. first electron affinities +
4. lattice enthalpy

Question 19

successive electron affinities

Answer 19

when an anion has a greater charge than 1-, successive electron affinities are required
first EA: O(g) + e- –> O-(g)
second EA: O-(g) + e- –> O-2 (g)

Question 20

are ΔEA2H⦵ exothermic or endothermic

Answer 20

endothermic = a second electron is being gained by a negative ion, which repels the electron away, so energy must be put in to force the negatively charged electron onto the negative ion

Question 21

successive ionisation energies

Answer 21

for (Mg)2+ there is a 2+ charge so two ionisation energies need to included