Thermodynamics

Question 1

Define enthalpy of lattice formation

Answer 1

The enthalpy change when one mole of a crystalline compound is formed from gaseous ions scattered on infinite distance apart
(It is always exothermic process)

Question 2

What is the formula to represent the enthalpy lattice formation?

Answer 2

M+(g) + X-(g) —> MX(s)

Question 3

Define enthalpy of lattice dissociation?

Answer 3

The enthalpy change when one mole of lattice is broken up to produce gaseous ions in infinite distance apart

(It is an endothermic process)

Question 4

What is the formula to represent the amount enthalpy of lattice dissociation

Answer 4

MX(s) —> M+(g) + X-(g)

Question 6

The value of lattice enthalpy depends on?

Answer 6

1. The charges in the ions
2. The size of the ions
3. The type of lattice formed

Question 7

It’s impossible to measure lattice enthalpies directly however we can use Born Haber cycles. To do this for an ionic compound what data do you need?

Answer 7

1. Enthalpy of formation
2. Ionisation energy
3. Enthalpy of atomisation
4. Bond enthalpy
5. Electron affinity

Question 8

Define enthalpy of formation.

Answer 8

Energy released during the formation of one mole of a compound from its elements in their standard enthalpy of formation

Question 9

The value of lattice enthalpies of formation will be higher if…

Answer 9

1.The ions are smaller
2. The ions have a greater charge

Question 10

What are the standard conditions in which enthalpy of formation should be calculated?

Answer 10

Temperature at 298K
And pressure in 100kpa