Question

A reaction A(aq)+B(aq)<-->C(aq) has a standard free-energy change of –3.35 kJ/mol at 25 °C. What are the concentrations of A, B, and C at equilibrium if, at the beginning of the reaction, their concentrations are 0.30 M, 0.40 M, and 0 M, respectively?

Answer 1

dG = -RTlnK. Solve for K. Then

.......A + B ==> C
I..0.30.0.0.40...0
C....-x....-x....x
E..0.30-x..0.40-x..x

Substitute the E line into Keq expression and solve for x, then evaluate concn A and B.
Don't forget to use dG in J/mol and not kJ/mol

Answer 2

.298, .398, .00177