*This preview shows
page 1. Sign up
to
view the full content.*

**Unformatted text preview: **um towards
products, removing reactants or adding products drives the equilibrium towards
reactants. Temperature Dependence of Equilibrium Constants
From Chapter 4, we have
é ¹ æ ,G ö ù = − ,H .
ë ¹T è T ø û P
T2 (4.69) Since ,G = −RT ln K ,substituting for ∆G°, we get
P
æ ¹ ln K ö j d ln K = ,H .
Pø
P
è ¹T
RT 2
dT
P (4.71) The approximate equality holds in most cases because K°P typically has a very
weak dependence on P and a very strong dependence on T. On rearranging and
integrating, we get
ln K = − ,H + const.
P
RT (4.75) which implies that when ln(K°P) is plotted as a function of 1/ T, the slope will be
equal to –∆H°/R. However, we also know that ∆G° = ∆H° – T∆S°. Therefore, we
get
S
ln K = − ,G = − ,H + ,R .
P
RT
RT (4.76) Comparing Eqs. (4.75) and (4.76), we see that if ∆H° is independent of
temperature, the intercept of the line will be equal to the entropy change for the
process.
It is also possible to show that
æ ¹ ln K ö j d ln K = ,U .
Cø
C
è ¹T
RT 2
dT
P...

View
Full
Document