lattice enthalpy Flashcards
1
Q
Define lattice enthalpy
- its use
A
formation of 1 mol of an ionic lattice from it constituent gaseous ions under standard conditions (298K and 100kPa)
- measure of ionic bond strength
- more -ve LE, stronger the bonding
2
Q
define Enthalpy change of formation
A
- energy transferred when
- 1 mole of a compound is formed from its elements under standard conditions (298K, 100kpa)
- all reactants and products being in their standard states
3
Q
define enthalpy change of atomisation
A
- the enthalpy change when
- 1 mole of gaseous atoms is formed
- from it’s element in its standard state
- endothermic bc bonds are broken
4
Q
define first Ionisation enthalpy
A
- enthalpy change required to
- remove 1 mole of electrons
- from 1 mole of gaseous atoms
- to form 1 mole of gaseous ions
- with a +1 charge
- endothermic - energy needed to overcome attraction
5
Q
define first electron affinity
A
- enthalpy change that occurs when
- 1 mole of gaseous atoms
- gain 1 mole of electrons
- to form 1 mole of gaseous ions
- with a –1 charge
- exothermic - e- added attracted to nucleus.
6
Q
Define Enthalpy of Hydration
A
- Enthalpy change when
- gaseous ions dissolve in water
- to form one mole of aqueous ions
7
Q
define Enthalpy of solution
A
- enthalpy change when
- one mole of a solute
- dissolves in a solvent
8
Q
experimental determination of EC of formation
A
- calc energy change in kj
- q = m(J) x c(4.18) x ΔT(K)
- ANS/1000 to get in kj
- calculate moles of solid in question
- calc ΔsolH of 1mol of solid by doing:
- q/n
9
Q
describe the dissolving process
A
- ionic lattice breaks up
- water molecules are attracted to and surround the ions
10
Q
properties of ionic compounds
A
- high MP/BP
- soluble in polar solvents
- conduct electricity when molten/aq
11
Q
ionic size effect on LE
A
- ionic radius inc
- attractions between ions decreases
- LE is less negative
- MP decreases
12
Q
ionic charge effect on LE
A
- ionic charge inc
- attraction between ions inc
- LE becomes more negative
- MP inc
