Chemistry Thermodynamics Math Question 8

Question

At 25 C, the partial pressure of CO₂(g) in a bottle of soda water is 2.2 bar. Calculate the equilibrium concentration of dissolved carbon dioxide under these conditions. The standard Gibbs free energy of formation of CO₂(aq) is -386. kJ/mol and Δ_fG⁰[CO₂(g)] = -394.4. kJ/mol.

Answer 1

CO₂(g) <==> CO₂(aq)

∆G_rxn = -386 kJ/mol - (-394.4 kJ/mol) = 8.4 kJ/mol

ln Keq = -∆G/RT = -8.4/(8.314)(298)

ln Keq = -0.00339

Keq = 0.9966 = Kp

Kp = P_CO2(aq) / P_CO2(g)

0.9966 = P_CO2(aq) / 2.2 bar

P_CO2(aq) = 2.2 bar