Enthalpy changes Flashcards
What are the units for enthalpy changes?
kJ mol -1
What are standard conditions?
100 kPa
Stated temp, usually 298K
Do exothermic reactions have a positive or negative enthalpy change?
Negative enthalpy change
Do endothermic reactions have a positive or negative enthalpy change?
Positive enthalpy change
How can lattice enthalpy be defined?
Lattice formation enthalpy
Lattice dissociation enthalpy
What is lattice formation enthalpy?
The enthalpy change when 1 mole of a solid ionic compound is formed from it’s gaseous ions
What is lattice dissociation enthalpy?
The enthalpy change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions
Is lattice formation negative or positive enthalpy change?
Negative
Is lattice dissociation negative or positive enthalpy change?
Positive
Define enthalpy change of formation.
The enthalpy change when 1 mole of a compound is formed from its elements in their standard states
Define the bond dissociation enthalpy.
The enthalpy change when all of the bonds of the same type in 1 mole of gaseous molecules are broken
Define enthalpy change of atomisation of an element.
The enthalpy change when 1 mole of gaseous atoms is formed 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 to gaseous atoms
Define the first ionisation energy.
The enthalpy change when 1 mole of gaseous +1 ions is formed from 1 mole of gaseous atoms
Define the second ionisation energy
The enthalpy change when 1 mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions
Define first electron affinity
The enthalpy change when 1 mole of gaseous 1- ions is made from 1 mole of gaseous atoms
Define second electron affinity
The enthalpy change when 1 mole of gaseous 2- ions is made from 1 mole of gaseous 1- ions
Define enthalpy change of hydration
The enthalpy change when 1 mole of aqueous ions is formed from gaseous ions
Define enthalpy change of solution
The enthalpy change when 1 mole of an ionic substance dissolves in enough solvent to form an infinitely dilute solution
What is Cl2(g) -> 2Cl(g) an example of?
Bond dissociation enthalpy
What is 1/2 Cl2(g) -> Cl(g) an example of?
Enthalpy change of atomisation of an element
What is NaCl(s) -> Na(g) + Cl(g) an example of?
Enthalpy change of atomisation of a compound
What is Mg(g) -> Mg+1 (g) + e- an example of?
First ionisation energy
What is Mg+1 -> Mg+2 (g) + e- an example of?
Second ionisation energy
What is O(g) + e- -> O-(g) an example of?
First electron affinity
What is O-(g) +e- -> O2-(g) an example of?
Second electron affinity
What is Na (g) -> Na (aq) an example of?
Enthalpy change of hydration
What is Ca(s) + Cl2 (g) -> CaCl2(s) an example of?
Enthalpy change of formation
