Lattice Enthalpy

Question 1

Lattice enthalpy, ΔHθLE

Answer 1

enthalpy change when one mole of ionic solid is formed from its gaseous ions under standard conditions

M+(g) + X-(g) -> MX(s)

Question 2

Enthalpy change of formation, ΔHθf

Answer 2

enthalpy change when one mole of a compound is made from its constituent elements in their standard states under standard conditions

Question 3

What are standard conditions?

Answer 3

298K, 100kPa

Question 4

Enthalpy change of atomisation, ΔHθatom

Answer 4

enthalpy change required to produce one mole of gaseous atoms from the element in its standard state

Na(s) -> Na(g)
1/2O2(g) -> O(g)

Question 5

First ionisation energy, ΔHθ IE1

Answer 5

the energy required to remove an electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

Question 6

First electron affinity, ΔHθ EA1

Answer 6

the energy change associated with converting one mole of gaseous atoms of an element to one mole of singly charged gaseous negative ions

X(g) + e- -> X-(g)

Question 7

electron affinity - exo or endo?

Answer 7

1st - ALWAYS EXO

2nd onwards - ALWAYS ENDO

Question 8

lattice enthalpy is an indication of…

Answer 8

the strength of the electrostatic attraction between the ions in the solid compound.

• the more negative ΔHθLE, the stronger the bonds

Question 9

lattice enthalpy - exo or endo?

Answer 9

ALWAYS EXO

– because ionic bonds are FORMED so energy is released to the surroundings

Question 10

enthalpy change of solution ΔsolH

Answer 10

dissolving one mole of solute completely under standard conditions

Question 11

enthalpy change of hydration ΔhydH

Answer 11

dissolving one mole of gaseous ions in water to form one mole of aqueous ions under standard conditions

Question 12

strength of ionic bonding (and increasing negativity of ΔHθLE) increases with…

Answer 12

increasing ionic charge

decreasing ionic radius

Question 13

entropy, S, JK-1mol-1

Answer 13

measure of the dispersal of energy in a system

Question 14

arrange in increasing entropy:

liquid, solid, gas, plasma, solution

Answer 14

Solid
Liquid
Solution
Gas
Plasma

Question 15

entropy is always

Answer 15

positive

Question 16

entropy increases when the moles of gas

Answer 16

increases

Question 17

ΔS=

Answer 17

∑Sproducts -∑Sreactants

Question 18

what is more favoured, reactions with -ΔS or +ΔS? why?

Answer 18

+ΔS as more disorder is created

Question 19

what sign of ΔG means that a reaction is ‘feasible’?

Answer 19

-ΔG

Question 20

ΔG=

Answer 20

ΔH -TΔS

Question 21

unit of ΔG

Answer 21

kJmol-1

Question 22

unit of ΔH

Answer 22

kJmol-1

Question 23

normal unit of ΔS

Answer 23

JK-1mol-1

Question 24

unit of T

Answer 24

K

Question 25

what must we change the unit of ΔS to to make the equation for free energy work?

Answer 25

kJK-1mol-1