entropy and gibbs free Flashcards
1
Q
to find the change in entropy
A
using aA+bB = cC+dD change in entropy = cSf(C) + dSf(D) - aSf(A) - bSf(B) where; a,b,c,d= stoichiometric coefficients Sf= standard entropy of formation
2
Q
unit for change in entropy
A
J/K
3
Q
unit for entropy
A
J/mol. K
4
Q
change in entropy for phase change
A
q/T
where q=heat
T is temperature in K
q = m . heat of phase change
5
Q
Gibbs free energy
A
determines if reaction goes spontaneously or not
D = delta
DG = DH - TDS
where DG = Gibbs free DH = enthalpy DS = entropy T = temperature
6
Q
how to know if reaction is spontaneous
A
if DG = 0 it is in equilibrium
DG > 0 it is not spontaneous
DG< 0 it is spontaneous
7
Q
to find DH
A
Heat of formation for products - heat of formation for reactants.
N.B: there is no heat of formation for elements do its 0.
8
Q
Relationship between DG and K
A
DG=-RTInK
