MEMORISE Flashcards
what is the () Ssurrounding equation
ENTROPY
() Surrounding = -()H/ T
what is the ()Ssystem equation
Products-Reactants
what is the ()Stotal equation
System + Surrounding
what is Gibbs free energy equation
()G = ()H - T ()S
s is system here
when is Gibbs reaction FEASIBLE
is G is NEGATIVE
is G = 0 the reaction is JUST feasible
whats another equation for Gibbs with lnK
()G = -RTlnK
define enthalpy change of formation
the energy transferred when 1 mole of the compound is formed from its elements under standard conditions (298 and 200kpa), w all reactants and products being in standard states
Na(s) + 1/2Cl2 —> NaCl
define enthalpy of atomisation
the enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state
Na(s) —> Na(g)
define 1st ionisation enthalpy
the enthalpy change required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a 1+ charge
Mg(g) —-> Mg+ (g) + e-
define 2nd ionisation enthalpy
the enthalpy change required to remove 1 mole of electrons from 1 mole of 1+ ions to produce 1 mole of gaseous 2+ ions
Mg+(g) —> Mg2+ (g) + e-
define 1st electron affinity
the enthalpy change that occurs when 1 mole of gaseous atoms gain 1 mole of electrons to form 1 mole of gaseous ions with a 1- charge
O(g) + e- —> O-
why is the 1st electron affinity always exothermic for atoms that normally form negative ions?
because the ion is more stable than the atom and there is attraction between the nucleus and electron
define 2nd electron affinity
the enthalpy change when 1 mole of gaseous 1- ions gain 1 electron per ion to produce gaseous 2- ions
O-(g) + e- —> O2-
Why is the 2nd electron affinity for oxygen endothermic?
because it takes energy to overcome the repulsive force between the negative ion and the electron
define enthalpy change of lattice formation
the standard enthalpy change when 1 mole of an ionic crystal lattice is formed from its constituent ions in gaseous form
Na+ (g) + Cl-(g) —> NaCl (s)
define enthalpy of solution
the standard enthalpy change when 1 mole of an ionic solid dissolves in a large amount of water to ensure that the dissolved ions are separated and do not interact with one another
NaCl (s) + aq —> Na+ (aq) + Cl-(aq)
define enthalpy of hydration
enthalpy change when 1 mole of gaseous ions become hydrated such that further dilution causes no further heat change
X+(g) + aq —> X+ (aq)
ALWAYS EXOTHERMIC as bonds are made between ions and water molecules
