chapter 18 pt 3 Flashcards
(20 cards)
Gibbs free energy is the maximum amount
of work energy that can be released to the surroundings by a system at constant pressure and temp
Gibbs free energy is also called
because it is analogous to storing
chemical potential
energy in a mechanical system
ΔS univ is positive when spontaneous so ΔG is
negative when spontaneous
ΔS and ΔG can both be used to determine
spontaneity
nonspontaneous reactions are
reactant favored
spontaneous reactions are
product favored
change of Gibbs free energy for process at constant pressure and temp is
ΔS univ= -ΔG/T
at constant pressure and temp a process will be spontaneous only if
ΔG is negative
ΔH (-) and ΔS (+) than
at low and high temps ΔG <0 thus spontaneous
ΔH (+) and ΔS (-) than
at low and high temps ΔG >) thus nonspontaneous
ΔH (-) and ΔS (-) than
at low temps ΔG <0 spontaneous
at high temps ΔG > 0 nonspontaneous
ΔH (+) and ΔS (+) than
at low temps ΔG > 0 nonspontaneous
at high temps ΔG <0 spontaneous
the sign in free energy depends on
temperature
change in enthalpy is negative meaning heat is emitted to the surroundings making
the entropy of the system positive and the reaction exothermic
entropy of the system decreases liquid ->
to solid
change in enthalpy is positive meaning heat is absorbed by the system making the
reaction endothermic and entropy of the surroundings is negative
entropy of system increases from liquid ->
to gas
third law of thermodynamics says that
the entropy of a perfect crystal at absolute zero is 0
any substance that isn’t a perfect crystal at zero
has some energy from entropy
sign of entropy of any substances at temperatures
above zero is always positive
