Question

If pyrophosphoric acid (H4P2O7) and arsenous acid (H3AsO3) have acid dissociation constants of 3.0*10^-2 and 6.6*10^-10, respectively, at room temperature, find the Gibbs Free energy of each dissociation reaction.

Answer 1

Solution :-

formula to calculate the Gibbs free energy is as follows

Delta G = -RT ln K

T= temeprature in kelvin ( 298 K)

lets calculate the Gibbs free energy for the H4P2O7

Delta G = -RT ln K

            = - 8.314 J per mol K * 298 K * ln (3.0*10^-2)

            = 8.7*10^3 J

8.7*10^3 J * 1 kJ / 1000 J = 8.7 kJ

now lets calculate the Gibbs free enegy for the H3AsO3

Delta G = -RT ln K

           = -8.314 J per mol K * 298 K * ln (6.6*10^-10)

          = 5.24*10^4 J

5.24*10^4 J * 1 kJ / 1000 J = 52.4 kJ