Lattice enthalpy Flashcards
What is lattice enthalpy?
The enthalpy change that accompanies the formation of one mole of an ionic lattice compound from its gaseous ions under standard conditions
What is lattice enthalpy a measure of?
Strength of ionic bonding in a giant ionic lattice
What type of enthalpy change is lattice enthalpy always?
Exothermic - it always has a negative value
What is a Born-Haber cycle?
An energy cycle used to determine lattice enthalpy
What is standard enthalpy change of atomisation?
The enthalpy change that takes place for the formation of one mole of gaseous atoms from the element in the standard state, under standard conditions
What is first ionisation energy?
The enthalpy change required to remove one electron from each atom in mole of gaseous atoms to form one mole of gaseous +1 ions
Are ionisation energies endothermic or exothermic?
Endothermic
What is the first electron affinity?
The enthalpy change that takes place when one electron is added to each atom in mole of gaseous atoms to form one mole of gaseous 1- ions
Are first electron affinities exothermic or endothermic?
Exothermic
What is required if an anion has a greater charge than -1, such as O 2-?
Successive electron affinities are required
Are second electron affinities endothermic or exothermic?
Endothermic
What is the Born-Haber cycle for magnesium oxide?
What are the calculations you’d for the magnesium oxides Born-Haber cycle?
Why may enthalpy values need to be halved or doubled in lattice enthalpy calculations?
Depending on the moles of elements in the ionic solid involved
What is enthalpy change of solution?
The enthalpy change that takes place when one mole of an ionic substance dissolves in sufficient water to form an infinitely dilute solution
Is enthalpy change of solution endothermic or exothermic?
Either
What is enthalpy change of hydration?
The enthalpy change when 1 mole of a specified gaseous ion dissolves in sufficient water to form an infinitely dilute solution
Are hydration enthalpies endothermic or exothermic?
Exothermic
What 2 processes take place when a solid ionic compound dissolves in water?
- The ionic lattice is broken up forming separate gaseous ions (opposite of lattice enthalpy)
- The separate gaseous ions interact with polar water molecules to form hydrated aqueous ions. The energy change involved is the enthalpy change of hydration
What is the equation for enthalpy of solution?
Enthalpy of solution = reverse lattice enthalpy + hydartion enthalpy
What is the equation for enthalpy of solution?
Enthalpy of solution = reverse lattice enthalpy + hydration enthalpy
What is the energy cycle between gaseous ions, aqueous ions and an ionic lattice?
How do you find the total Δhyd H?
Add together the Δhyd H values of both anions and cations together
What are the effects of ionic charge on lattice enthalpy?
- Ionic charge increases
- Attraction between ions increases
- Lattice energy becomes more negative
- Melting point increases - lattice enthalpy incdreases
What are the effects of ionic size on lattice enthalpy?
- Ionic radius increases
- Attraction between ions decreases
- Lattice enthalpy less negative
- Melting point decreases - lattice enthalpy decreases
What are the affects of ionic charge on hydration?
- Ionic charge increases
- Attraction with water molecules increases
- Hydration energy becomes more negative
What are the effects of ionic size on hydration?
- Ionic radius increases
- Attraction between ion and water molecules decreases
- Hydration energy less negative
