In: Chemistry
At equilibrium for reaction 1, in which substrate A is converted to product B, there is 4 times as many molecules of A as there are molecules of B. At equilibrium for reaction 2, in which substrate R is converted into product S, there is 8 times as many molecules of S as there are molecules of R. If these two reactions are coupled, what is the net standard free energy change?
A ----------------------> B
1 4
K1 = 4 /1 = 4
Go = -RT lnK
= - 8.314 x 10^-3 x 298 x ln 4
= - 3.43 kJ/mol
R -----------------------> S
8 1
K2 = 1/8 = 1/ 8
Go = -RT lnK = -8.314 x 10^-3 x 298 x ln 1/8 = 5.15 kJ/mol
for coupled reaction
Go = -3.43 + 5.15
Go = 1.72 kJ/mol