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thermodynamics: entropy and gibbs free energy - Coggle Diagram
thermodynamics: entropy and gibbs free energy
spontaneity
processes that are spont in one direction are not spont in the other direction
you need the gibbs free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) to tell if the rxn is spont or not
entropy change, S
the measure of the number of ways in which matter can be arranged and energy can be distributed in a system
(measure of the no. of possibilities of arrangement)
FACTORS
change in no. of gaseous particles
more particles, ΔS increase
mixing of particles (no rxn)
more ways to arrange the particles, ΔS increase
change in phase
decreasing ΔS: gas > liq > sol
change in temp
temp increase, more KE, ΔS increase
Gibbs free energy, G
ΔG = ΔH - TΔS (units: kJ/mol or J/mol)
prediction of spontaneity
ΔG > 0
not spont in the forward direction, spont in the reverse direction
ΔG < 0
spont in the forward direction, not spont in the reverse direction
ΔG = 0
both forward and backward are spont
system has reached
dynamic equilibrium
, no net change in amt of products and reactants
four cases (T in Kelvins is always +ve)
ΔH -ve and ΔS +ve, ΔG < 0 always spont
ΔH +ve and ΔS -ve, ΔG > 0 never spont
ΔH +ve and ΔS +ve, ΔG < 0 at high T, only spont at high T
ΔH -ve and ΔS -ve, ΔG < 0 at low T, spont only at low T
crossover temperature
where ΔG = 0 when ΔH and ΔS are both +ve
assumptions when calculating
ΔS and ΔH remain constant at all temps
(only true as long as no phase change)