Standard enthalpy change of formation(ΔHf): The enthalpy change when one mole of a compound is formed from its elements under standard conditions
Enthalpy change of combustion (ΔHc): enthalpy change which occurs when one mole of the compound is burned completely in oxygen under standard conditions
Born-Haber Cycle is used to find the lattice enthalpy
Lattic enthalpy: the change in enthalpy that occurs when one mole of a solid compound is seperate into it gaseous form under standard conditions
MX(s) > M⁺(g) + X⁻(g) ∆Hlat >0
Enthalpy of atomization: the standard enthalpy change that occurs on the formation of one mole of seperate gaseous atoms of an element in its standard state
M(s) > M(g)∆Hat >0
1/2X2 (g) > X(g)∆Hat > 0
Ionization Energy: is the standard enthalpy change that occurs on the removal of 1 mol of electrons from 1 mol of atoms or positively charged ions in the gaseous state. For metal ions with multiple valence electrons there can be multiple ionization energies
M(g) > M⁺(g) + e⁻ ∆Hie >0
Electron affinity: is the standard enthalpy change on the addition of 1 mol of electrons to 1 mol of atoms in the gaseous phase
X(g) + e⁻ > X⁻ ∆Hea <0
Constructing the Born-Haber cycle
The born-haber cycle combines the lattic enthalpy, enthalpy of atomization, ionization energy, and the electron affinity to find the enthalpy of formation of an ionic compound
The different changes in enthalpy get added together
Generalized Born-Haber Cycle
A) ∆Hie
B) ∆Hat (X)
C) ∆Hat (M)
D) ∆Hea (X)
E) ∆Hlat
F) ∆Hf
Variation in lattice enthalpy values
An increase in the ionic charge will result in a greater attraction between opposing charge ions increase the lattice enthalpy
A the distance between the bonded ions increases, the strength of the electrostatic attraction decreases, decreasing the lattice enthalpy
Enthalpy of solution : the change in ethalpy that ocurs when one mole of a solute (ionic compound) is dissolved to form aqueous ions in an infinitely dilute solution under standard conditions
MX(s) > M⁺(aq) + X⁻(aq) ∆Hsol usually >0
Enthalpy of hydration: the change in enthalpy that occurs when 1 mole of gaseous ions is dissolved in water to form an infinitely dilute solution of one mole of aqueous ions under standard conditions
M⁺(g) > M⁺(aq) ∆Hhyd <0
X⁻(g) > X⁻(aq) ∆Hhyd <0
Solvation is used in pae of hydration for solvents other than water
The lattice enthalpy, enthalpy of hydration, and enthalpy of solution form a cycle