D. We have missed something in this analysis. As more 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 α-D-glucose and the β-D-glucose mix, the entropy of the system increases by
ΔS_mix = -Nk_Bx ln x - Nk_By ln y
where x is the fraction of β-D-glucose and y is the fraction of α-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".
1. Determine an improved expression for the "total" Gibbs free energy change ΔG_total by adding the contribution due to this change in entropy to the ΔG_a(x) you found before (Hints: Recall that entropy contributes to G by the term -TΔS. Also, make sure all terms have the same units!).