Thermodynamics

Question 1

Lattice enthalpy values are affected by:

Answer 1

The size of the ionic radius
- The larger the ionic radius, the less exothermic (closer to 0) the lattice enthalpy
- Because the attraction between the outer electrons and positive nuclei decreases as radius increases

The charge of the ions
- The greater the charge, the more exothermic (more negative) the enthalpy of lattice formation

Question 2

The perfect ionic model assumes that:

Answer 2

Ions are point charges
- Ions are perfect spheres
- Only electrostatic attractions occur between ions (only ionic bonding)
- The bonds have no covalent character

Question 3

Theoretical lattice enthalpy values based on the perfect ionic models are therefore usually smaller than those calculated using a Born-Haber cycle
Why?

Answer 3

Because covalent bonds are stronger than ionic bonds

Question 4

Enthalpy of hydration,

Answer 4

enthalpy change when one mole of gaseous ions are converted into
aqueous ions (an aqueous solution)

Question 5

Enthalpy of solution, ΔsolHθ

Answer 5

enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart not to interact with each other