Question
=-1.15K(J)/(m)ol C. The quoted value of Delta G_(alpha ->beta )=G_(beta )-G_(alpha )=-1.43k(J)/(m)ol corresponds to alpha -D-glucose ending in a state of 100%beta -D-glucose, meaning
=-1.15K(J)/(m)ol
\ C. The quoted value of
\\\\Delta G_(\\\\alpha ->\\\\beta )=G_(\\\\beta )-G_(\\\\alpha )=-1.43k(J)/(m)ol
corresponds to
\\\\alpha
-D-glucose ending in a state of
100%\\\\beta
-D-glucose, meaning
G_(initial )=G_(\\\\alpha )
while the
G_(final )=G_(\\\\beta )
. If instead only a fraction
x
ends up as
\\\\beta
-D-glucose while the rest
(1-x)
ends as
\\\\alpha
-D-glucose then
G_(final )=xG_(\\\\beta )+(1-x)G_(\\\\alpha )
.\ Use this to find
\\\\Delta G
if, starting with
100%\\\\alpha -D
-glucose only
(1)/(5)
of it ends up as the
\\\\beta -D
form.\ 2\ Let's analyze the possibility of equilibrium in this process. For the general case where only a fraction
x
of the
\\\\beta
-D-glucose ends in solution, determine the change
\\\\Delta G_(\\\\alpha ->\\\\beta )(x)
in Gibbs free energy. Pick a few
x
values and plot the function.\ According to your plot, for what fraction
x
would the Gibbs free energy reach its smallest value?\ D. We have missed something in this analysis. As more
\\\\beta
-D-glucose is converted, a different type of entropy change becomes crucial: the entropy of mixing. You derived an expression for this entropy change in Written Homework 4 (for the mixing of two gases, but the result applies equally here): as the
\\\\alpha
-D-glucose and the
\\\\beta
-D-glucose mix the entropy of the system increases by\
\\\\Delta S_(mix )=-Nk_(B)xlnx-Nk_(B)ylny
\ where
x
is the fraction of
\\\\beta
-D-glucose and
y
the fraction of
\\\\alpha
-D-glucose in the solution (they add up to 1). Recall that the total number of particles here is
N=N_(A)
as we are handling quantities "per mol".\ Determine an improved expression for the "total" Gibbs free energy change
\\\\Delta G_(total )
by adding the contribution due to this change in entropy to the
\\\\Delta G_(\\\\alpha ->\\\\beta )(x)
you found before (Hints: Recall that entropy contributes to
G
by the term - TS. Also, make sure all terms have the same units!).
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