12B: Lattice energy

ionisation

• 1 mole of gaseous atoms loses e^-

• 1st and 2nd endo

electron affinity

• 1 mole of gaseous atoms gains e^-

• 1st - exo, 2nd - endo

enthalpy of atomisation

• 1 mole of gaseous atoms produced

• from element in standard state

• endo

hydration enthalpy

• 1 mole of gaseous ions is hydrated (dissolved)

• …(g) + aq → …(aq)

• exo

enthalpy of solution

• 1 mole of gaseous ionic solid dissolves so that ions are separated

• …(s) + aq → …(aq) + …(aq)

bond dissociation enthalpy

• 1 mole of covalent bonds is broken

• in gaseous state

• …₂ (g) → 2…(g)

• endo

lattice enthalpy of formation

• 1 mole of ionic solid is formed

• from ions in gaseous state

• …(g) + …(g) → …(s)

• exo

lattice enthalpy of dissociation

• 1 mole of ionic solid is broken up

• into ions in gaseous state

• …(s) → …(g) + …(g)

• endo

enthalpy of vaporisation

• 1 mole of liquid turned into gas

• exo

enthalpy of fusion

• 1 mole of solid turned into liquid

• endo

Born-Haber cycle

1. formation ↓

2. atomisation ↑

3. ionisation (1st, 2nd) ↑

4. e^- affinity (1st, 2nd) ↑

5. lattice enthalpy of formation ↓

does the sign of S [system] make sense

• disorder increases/decreases

• as no. of molecules/moles increases/decreases

advantages and disadvantages of using t higher than … in Haber process

• rate of reaction is higher

• more … produced in given time

• at higher t S [surr] is less +ve (decreases)

• S [total] more -ve

• Kp decreases

• eq position moves further right/left

effect of charge and size of ion on lattice energy

• (compound) more exo

• (ion) larger than (ion)

• charges on ions are the same

• (ion) forms stronger attractions