1.8 Thermodynamics Flashcards
What is the enthalpy of atomisation?
The enthalpy change when one mole of gaseous atoms is formed from the element in its standard states under standard conditions.
What is the enthalpy of hydration?
The enthalpy change when 1 mole of gaseous ions is converted into aqueous ions.
What is the 1st electron affinity?
The enthalpy change when 1 mole of gaseous atoms is converted into 1 mole of gaseous ions (with a single 1- charge).
What is the 2nd electron affinity?
The enthalpy change when 1 mole of gaseous (-1) ions is converted into 1 mole of gaseous ions (-2).
What is the enthalpy of lattice dissociation?
Enthalpy changes when 1 mole of solid ionic compound dissociates into its gaseous ions.
What is the enthalpy of lattice formation?
Enthalpy changes when 1 mole of gaseous ions forms a solid ionic compound.
What is bond enthalpy?
The enthalpy change is required to break a covalent bond in a gaseous state.
What is the enthalpy of formation?
The enthalpy change when 1 mole of a substance is formed from its constituent elements under standard conditions, with all reactants and elements in their standard states.
What is the enthalpy of combustion?
The enthalpy change when 1 mole of a substance is completely burned in oxygen in standard condition, with all the constituent reactants and products in their standard states.
How do you set up and form a Born-Haber cycle?
- Start with the reactants in their standards state (as enthalpy of formation).
- Make these reactants into gaseous atoms, by the enthalpy of atomisation.
- Make these gaseous atoms into ions, by the ionisation energy / electron affinity.
- Ions are used to form lattice formation.
How to draw the Born-Haber cycle?
ionic lattice ← formation → atomisation → ionisation energy → lattice formation (ends with ionic lattice)
What is the perfect ionic model?
Ions are point charges, perfect spheres, and are attracted only by electrostatic forces of attraction. There is no covalency.
Why do some compounds have different theoretical vs experimental enthalpy values?
Some ionic bonding has covalent nature due to polarisation. This is a result of smaller ions attracting electrons from bigger ones, as they are more electronegative. This goes against the perfect ionic model.
- The theoretical values are based on the perfect ionic model, so experimental values are different.
What’s the equation of the enthalpy of hydration?
Enthalpy lattice dissociation + Sum of hydration enthalpies
What is entropy?
The disorder of a reaction, the ‘randomness’.
