Lattice enthalpy and Free Energy Flashcards
What is lattice enthalpy?
The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.
Symbol is ΔLeH
Is lattice enthalpy -ve or +ve?
Negative as bonds are being formed
What is the Born-Haber cycle?
A cycle that you can calculate lattice enthalpy from
What is the definition of standard enthalpy change or atomisation?
The enthalpy change that takes place for the formation of one mole of gaseous atoms from the element in its standard state under standard conditions.
Symbol is ΔatH
What is the definition of 1st electron affinity?
The enthalpy change that takes place when one electron is added to
each atom in one mole of gaseous atoms of an element to form one
mole of gaseous 1- ions.
Symbol: ΔeaH
What is the general idea of the Born-Haber cycle?
Lattice enthalpy = Sum of all enthalpy changes - Enthalpy of formation
What is standard enthalpy change of hydration?
The enthalpy change that takes place when one mole of isolated
gaseous ions is dissolved in water forming one mole og aqueous
ions under standard conditions.
Symbol: ΔhydH
What are the two main factors that effect ΔLeH
charge (ionic charge)
and
size (ionic radius)
What is entropy generally considered to be?
What is it’s symbol and units?
The term used for the dispersal of energy and disorder
within the chemicals making up the chemical system.
Symbol: S
Units: J K^-1 mol^-1
What is the order of entropy of states of matter (Lowest to highest)?
Solid —> Liquid —–> Gas ——-> Plasma
What does Gibbs energy / Free energy change (ΔG) tell us?
Whether or not a reaction is feasible and / or spontaneous
What is the equation for Gibbs energy / Free energy change?
ΔG = ΔH - TΔS
Change in enthalpy (kJ K^-1 mol^-1) - Temperature (K) x Change in entropy (J K^-1 mol^-1)
What must be done to the change in entropy in Gibbs energy / Free energy change calculations to make it consistent?
Divide it by 1000 to make it into kJ K^-1 mol^-1
What must ΔG be for a reaction to be feasible?
It must be <0 a.k.a negative
