Thermodynamics Flashcards
Define enthalpy change of formation.
The enthaply change when 1 mole of a compound is formed from its elements in their standard states under standard conditions.
Define lattice formation enthaply.
The enthaply change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions.
Define lattice dissociation enthalpy.
The enthaply change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions under standard conditions.
Define bond dissociation enthaply.
The enthaply change when all the bonds of the same type in 1 mole of gaseous molecules are broken.
Define enthalpy change of atomisation of an element.
The enthaply change when 1 mole of gaseous atoms is formes from an element in its standard state.
Define enthalpy change of atomisation of a compound.
The enthalpy change when 1 mole of a compound in its standard state is converted into gaseous atoms.
Define first ionisation enthalpy.
The enthalpy change when 1 mole of gaseous atoms is converted into 1 mole of gaseous ions each with a single positive charge.
Define second ionisation enthalpy.
The enthalpy change when 1 mole of gaseous ions each with a single positive charge are converted into 1 mole of gaseous ions each with a 2+ charge.
Define first electron affinity.
The enthalpy change when 1 mole of gaseous atoms is converted into 1 mole of gaseous ions each with a single negative charge.
Define second electron affinity.
The enthalpy change when 1 mole of gaseous ions each with is single negative charge is converted into 1 mole of gaseous ions each with a 2- charge.
Define enthalpy change of hydration.
The enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions.
Define the enthalpy change of solution.
The enthalpy change when 1 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.
What assumptions do we make when using the perfect ionic model?
All ions a spherical, and their charge is evenly distrubuted around them.
What do we mean by ionic lattices having ‘covalent character’?
The ions aren’t perfectly spherical so positive ions can polarise negative ions, distorting their shape. This gives us partial covalent bonding.
How can we use Born-Haber cycles to give evidence for covalent character in ionic compounds?
Born-Haber cylces are made up of experimental values, and if the lattice enthalpy we achieve from these is much larger than that of the theoretical lattice enthalpy from the perfect ionic model, this shows us that the bonding is stronger, and there is covalent character in the bonding.
