3.1.8 Thermodynamics Flashcards
Enthalpy of formation
EC when 1 mole of compound formed from elements in standard states and conditions
Lattice enthalpy
Energy change when 1 mole of a solid ionic compound formed from its gaseous ions under standard conditions
Enthalpy of combustion
Enthalpy change when one mole of a substance is burned completely in oxygen under standard conditions
Atomisation Enthalpy
The energy required for the formation of a mole of gaseous atoms under standard conditions.
Enthalpy of Electron Affinity
The enthalpy change when one mole of electrons is added to a mole of gaseous atoms under standard conditions
How 2 Born-Haber cycle?
∆H (enthalpy of formation) = Everything else added (diagram)
What are two things you should be careful of when doing Born-Haber cycles?
- The direction of the right hand arrow
- The step to turn 1/2O2 into O
Enthalpy of hydration
The enthalpy change when one mole of gaseous ions is dissolved in water to form one mole of aqueous ions under standard conditions
Entropy increases…
- With temperature
- Change in state
How do you calculate entropy of a reaction?
Entropy of products - entropy of reactants
Gibbs Free-Energy equation
∆H-(Tx∆S/1000)
When is a reaction feasible?
When ∆G>0
Why is the theoretical and experimental value of lattice enthalpy different?
- Compound may have partial covalent character
- Theoretical value assumes perfect ionic bonding
Why is the electron affinity value negative?
- Attraction between nucleus and electrons
- Causes energy to be released
Why is hydration exothermic?
- Water is polar
- So ion is attracted to hydrogen/oxygen in water
- Causing energy to be released
