Calculate the value of ΔG in kJ at 298 K if the concentrations of Ca2+(aq) and CO32-(aq) are 0.356 and 0.255, M respectively.

Question

The value of ΔG^o for the precipitation reaction,

Ca²⁺(aq) + CO₃^2-(aq) <=> CaCO₃(s)

is -48.1 kJ at 298 K.

Calculate the value of ΔG in kJ at 298 K if the concentrations of Ca²⁺(aq) and

CO₃^2-(aq) are 0.356 and 0.255, M respectively.

My answer was -50.68 somehow

The correct answer is -42.16

Answer 1

ΔG_rxn = ΔG^ο_rxn + RT ln K = (-48100J/mol) + (8.314J/mol K)(298K)(ln(11)) = -48100J +5940J = -42159J

=42.16kJ

K=1/[Ca²⁺][CO₃^2-] = 1/[.356][.255]=11