thermodynamics

• enthalpy of lattice dissociation

  the enthalpy change to seperate one mole of solid ionic compound into its gaseous ions
• enthalpy of lattice formation

  the enthalpy change when one mole of solid ionic compound is formed from its gaseous ions
• standard enthalpy of formation

  the enthalpy change that occurs when one mole of a compound is formed from its constituent elements with all reactants and products in their standard states
• standard enthalpy of atomisation

  the enthalpy change when one mole of gaseous atoms is formed from the element in its standard state
• bond enthalpy

  the energy required to break one mole of a given covalent bond in the molecules in the gaseous state
• bond enthalpies are always

  endothermic- it takes energy to break
• first ionisation energy

  the energy needed to remove one mole of electrons from one mole of atoms in the gaseous state (always endothermic)
• second ionisation energy

  the enthalpy change when one mole of gaseous 2+ ions are formed from gaseous 1+ ions (always endothermic)
• first electron affinity

  the enthalpy change when one mole of gaseous 1- ions are formed from one mole of gaseous atoms (always exothermic)
• second electron affinity

  the enthalpy change when one mole of gaseous 2- ions are formed from one mole of gaseous 1- ions (always endothermic)
• perfect ionic model

  ions are perfect spheres with only electrostatic forces of attraction
• enthalpy of solution

  the enthalpy change when one mole of an ionic substance dissolves in enough solvent to form an infinitely dilute solution
• enthalpy of hydration

  the enthalpy change when one mole of aqueous ions is formed from one mole of gaseous ions (always exothermic)
• entropy is...

  a measure of disorder in a system. it is a measure of the number of ways that energy can be arranged. there is always a degree of disorder as particles always have energy, therefore the values for S are always positive
• $\Delta$S is favourable when


  it is positive
• $\Delta$H is favourable when 


  it is negative
• gibbs free energy change equation

  $\Delta G=$$\Delta H-T\Delta S$
• for a reaction to be feasible

  $\Delta G$ must be zero or negative ($\Delta G\le0$)
• to find the temperature that a reaction becomes feasible

  $T=$$\frac{\Delta H}{\Delta S}$ when $\Delta G=$$0$
• free energy graph

  y-axis= $\Delta G$

  x-axis= T

  intercept= $\Delta H$

  graient= -$\Delta S$