Ionic compounds

Question 1

What must be done to form a lattice?

Answer 1

• atomisation of metal
• atomisation of non metal
• ionisation of metal
• electron affinitiy of non metal
• formation of lattice

Question 2

How can a step of this process be calculated?

Answer 2

• Hess’s law tells us that the total enthalpy change for a chemical reaction is the same whatever route is taken
  
  • provided conditions are constant
• any quanitites can be claculated
  
  • using a Born-HAber cycle

Question 4

What is a Born-Haber cycle?

Answer 4

• a thermochemical cycle that includes all the enthalpy changews involved in the formation of an ioninc compound

Question 5

What do Born-Haber cycles begin with?

Answer 5

all elements in their standard states

0 enthalpy

Question 6

What are the steps of a Born-Haber cycle?

starting from the bottom left going clockwise

Answer 6

• atomisation of metal (2nd row bottom left)
• atomisation of non metal
• ionisation of metal
• electron affinity of non metal
• enthalpy of lattice formation

Question 7

Which ways do the arrows point?

Answer 7

• positive enthalpy change goes up

Question 8

What is the clockwise rule for Born-Haber cycle?

Answer 8

clockwise arrows = anticlockwise arrows

rearange to find desired value

Question 9

what is the perfect ionic model?

Answer 9

ions regarded as point charges

Question 10

why is the enthalpy of lattice dissociation for AgCl greater than observed value?

Answer 10

has some covalent characteristics

forces in lattice stronger than pure ionic attraction