Defined specifically for OCR A chemistry, focusing on lattice enthalpy and its significance in chemistry.
Key Concepts and Definitions
Enthalpy Change of Formation ((\Delta F H)): Change in enthalpy when one mole of compound is formed from its elements in their standard state under standard conditions.
Lattice Enthalpy of Formation: The enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions under standard conditions.
Ionization Energy: The enthalpy change when one mole of gaseous atoms loses an electron to form gaseous ions.
Ionic Bonding
The strength of an ionic bond depends on the charge and size of the ion.
Bigger charges and smaller ions lead to stronger electrostatic attractions, higher melting and boiling points.
Born-Haber Cycle
A methodical approach to understanding lattice enthalpies through visual diagrams representing various steps of ion formation and combination.
Demonstrates both exothermic and endothermic processes involved in forming ionic compounds.
Types of Enthalpy Changes
Formation: Exothermic, forming a solid compound from elements under standard conditions.
Ionization: Endothermic, removal of an electron from a gaseous atom.
Atomization: Endothermic, breaking down into atoms.
Lattice Enthalpy Calculations
Utilizes the Born-Haber cycle analogy, applying Hess's Law for calculating unknown lattice enthalpies.
Two routes can be taken, equivalent to reaching a destination via different paths, ultimately yielding the same energy change.
Enthalpy Change of Solution and Hydration
Solution: Dissolving an ionic substance in a solvent involves breaking bonds in the solute and forming new bonds with the solvent.
Hydration: The process where water molecules surround and interact with ions, significantly affected by ion charge and size.
Conclusion and Resources
Emphasizes the importance of understanding lattice enthalpy for OCR A chemistry.
Recommends utilizing additional resources like Alawi Chemistry YouTube channel for comprehensive exam preparation.