Enthalpy and Entropy Flashcards
Enthalpy change of reaction
Enthalpy change when:
* the molar quantitities expressed in the equation
* react under standard conditions
* In the given states
Enthalpy of combustion
Enthalpy change when:
* 1 mole of substance
* is burnt completely in oxygen
* Under standard conditions and in their standard states
Enthalpy of formation
Enthalpy change when:
* 1 mole of substance
* is formed from its pure elements
* Under standard conditions in the given states
Enthalpy of neutralisation
Enthalpy change when:
* 1 mole of water
* is formed from its pure elements
* Under standard conditions in the given states
Enthalpy of 1st ionisation energy
Enthalpy change when:
* 1 mole of atoms
* Lose 1 mole of electrons to form 1 mole of 1+ ions
* With all atoms in gaseous state
Enthalpy of 2nd ionisation energy
Enthalpy change when:
* 1 mole of 1+ ions
* Loses 1 mole of electrons to form 1 mole of 2+ ions
* With all ions in gaseous state
Bond enthalpy
Enthalpy change when:
* Breaking 1 mole of covalent bonds
* by homolytic fission
* in the gaseous state
Atomisation
- 1 mole of gaseous atoms
- formed from the element
- In standard states
1st Electron Affinity
- 1 mole of gaseous atoms
- Gains 1 mole of electrons
- to form 1 mole of 1- ions in the gaseous state
2nd Electron Affinity
- 1 mole of 1- gaseous ions
- gains 1 mole of electrons
- to form 1 mole of gaseous 2- ions
Lattice Enthalpy Association
- 1 mole of ionic solid
- being formed from its gaseous ions
Enthalpy of solution
Enthalpy change when:
* 1 mole of substance
* is dissolved in water
* to infinte dilution
Enthalpy of Hydration
Enthalpy change when:
* 1 mole of gaseous ions
* dissolved in water
* forming 1 mole of aqueous ions
Entropy
The measure of degree of disorder of a system
What is the free energy (ΔG) of a reaction at equilibrium
ΔG=0 for both forward and backward reactions to take place
What is the feasibility of reaction when ΔG is less than or equal to 0
Reaction is feasible or spontaneous
What is the feasibility of reaction when ΔG is greater than 0
Never feasible, reaction will not proceed
How does ΔG vary with temperature increases and how does feasiblity varies with temperature when ΔH is negative and ΔS is negative?
- TΔS becomes more negative so ΔG becomes more positive
- Feasible at low temperatures, decreasing feasibility
How does ΔG vary with temperature increases and how does feasiblity varies with temperature when ΔH is negative and ΔS is positive?
*TΔS becomes more positive so ΔG becomes more negative
*Always feasible
How does ΔG vary with temperature increases and how does feasiblity varies with temperature when ΔH is positive and ΔS is negative?
*TΔS becomes more negative so ΔG becomes more positive
*Never feasible
How does ΔG vary with temperature increases and how does feasiblity varies with temperature when ΔH is positive and positive?
*TΔS becomes more positive so ΔG becomes more positive
*Feasible at high temperatures, increasing feasibility
