5.2.1 Lattice Enthalpy: Module 5: Physical Chemistry & Transition Elements: Chemistry OCR A A Level

Define lattice enthalpy.

Formation of 1 mole of ionic lattice from gaseous ions under standard conditions.

What does a more exothermic lattice enthalpy mean?

More exothermic = More stronger ionic bonds

Why is it not possible to measure lattice enthalpy directly?

It is not possible to form 1 mole of ionic solid from its gaseous ions.

Define enthalpy change of solution.

Enthalpy change that takes place when 1 mole of a solute is completely dissolved in water under standard conditions.

Define enthalpy change of hydration.

The enthalpy change that takes place when dissolving one mole of gaseous ions in water.

What are the factors that impact the size of lattice enthalpy?

● Size of ions involved

● Charges on the ions

● Ionic bond strength

Which ions have more negative lattice enthalpy values? smaller / larger ions?Why?

Smaller ions because they can get closer hence more stronger attraction.

Describe hydration.

When a ionic lattice is broken the ions become part of the solution.

Positive ions get attracted towards slightly negative oxygen and negative ions get attracted towards slightly positive hydrogen.

What are the factors that impact the magnitude of the enthalpy of hydration?

● Size of the ion

● Charge on the ions