Lattice Energy

Question 1

enthalpy of atomisation

Answer 1

the enthalpy change when one mole of atoms is formed from its elements in their standard states under sc

Question 2

lattice energy

Answer 2

the energy change when 1 mole ionic compound is formed from its gaseous ions under sc

Question 3

1st electron affinity

Answer 3

the enthalpy change when one mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous ions with a 1 negative charge

Question 4

what are the factors that affect electron affinity

Answer 4

• greater nuclear charge, higher the EA
  
  • stronger attraction (affinity = attraction)
  • more energy released
• the smaller the atomic radius, higher the EA
• stronger attractive force between nucleus
• the smaller electron shells, higher EA
• less shielding from nucleus and outer shell electrons

Question 5

describe and explain the electron affinities of G 6 and 7

Answer 5

• less exothermic, lower EA, down the group
• F does not fit, such a small atomic radius
• very high electron density causes repulsion between electrons within atom
• hard for nucleus to attract other electrons

Question 6

explain ionic charge and ionic radius of lattice energy

Answer 6

As ionic radius decreases, lattice energy (add electron) increases
=higher charge density means there is a stronger electrostatic attraction forces

As ionic charge increases, lattice energy increases
=higher charge density (with other same size) so stronger attraction

Question 7

enthalpy hydration

Answer 7

enthalpy change when 1 mole of an gaseous ion are dissolved in sufficient water to form a dilute solution under sc / exo

Question 8

enthalpy solution

Answer 8

energy absorbed or released when 1 mole of an ionic solid dissolves in sufficient water to form a very dilute solution under sc / exo or endo

Question 9

explain ionic charge and ionic radius of enthalpy hydration

Answer 9

IONIC CHARGE = high charge density
-stronger ion-dipole attractions between water and ion

IONIC RADII = high charge density
-stronger ion-dipole attractions between water and ion

Question 10

thermal stability (ionic radius and polarisation)

Answer 10

more stable down the group (harder to decompose)

• ionic radius increase down the group so can polarise better
• can weaken C-O and form CO2, decompose better

Question 11

solubility and enthalpy solution (enthalpy and lattice energy)

Answer 11

-when ΔHsol have large positive values = insoluble
-since the lattice energy and ΔHhyd get less exo down a group
= Hess’s law shows ΔHsol is less exo
= more endo
= large positive values