Thermodynamics Flashcards
What does Hess’ Law state?
The enthalpy change for a reaction is independent of the route taken
Define standard enthalpy of formation
The enthalpy change when one mole of a compound is formed from its constituent elements in standard conditions, with all products and reactants in their standard states
What is the standard enthalpy of an element
0 by definition
Define standard enthalpy of combustion
The enthalpy change when one mole of a substance is completely burnt in (excess) oxygen
Define standard enthalpy of atomisation
Enthalpy change when one mole of gaseous atoms is formed from a compound in its standard state in standard conditions
Define first ionisation energy
Enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions
Define second ionisation energy
Enthalpy change when one mole of electrons is removed from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
Define first electron affinity
Enthalpy change when one mole of gaseous atoms gains one mole of electrons to form one mole of gaseous 1- moles
Define second electron affinity
Enthalpy change when one mole of gaseous 1- ions gains one mole of electrons to form one mole of gaseous 2- ions
Define lattice enthalpy of formation
Enthalpy change when one mole of solid ionic lattice is formed from its constituent gaseous ions
Define lattice enthalpy of dissociation
Enthalpy change when one mole of solid ionic lattice is dissociated into its gaseous ions
Define enthalpy of hydration
Enthalpy change when one mole of gaseous ions become hydrated / dissolved in water to infinite dilution [water molecules completely surround the ion]
Define enthalpy of solution
Enthalpy change when one mole of solute dissolves completely in a solvent to infinite dilution
Define mean bond dissociation enthalpy
Enthalpy change when one mole of (a certain type of) covalent bonds is broken, with all species in the gaseous state
Write an example equation for:
Standard enthalpy of formation
Standard enthalpy of combustion
Standard enthalpy of atomisation
- Mg (s) + 1/2 O2 (g) —> MgO (s)
- CH4 (g) + 2O2 (g) —> CO2 (g) + 2H2O (g)
- 1/2 I2 (g) —> I (g)
Write an example equation for:
First ionisation energy
Second ionisation energy
First electron affinity
- Li (g) —> Li+ (g) + e-
- Mg+ (g) —> Mg2+ (g) + e-
- Cl (g) + e- —> Cl- (g)
Write an example equation for
Second electron affinity
Lattice enthalpy of formation
Lattice enthalpy of dissociation
- O- (g) + e- —> O*2- (g)
- Na+ (g) + Cl- (g) —> NaCl (s)
- NaCl (s) —> Na+ (g) + Cl- (g)
Write an example equation for
Enthalpy of hydration
Enthalpy of solution
Mean bond dissociation enthalpy
- Na+ (g) —> Na+ (aq)
- NaCl (s) —> Na+ (aq) + Cl- (aq)
- Br2 (g) —> 2Br (g)