Chapter 16, Problem 16.111CHP

The standard free-energy change at 25 °C for the dissociation of water is 79.9 kJ:

$2{\text{H}}_{\text{2}}\text{O}\left(l\right)\rightleftharpoons {\text{H}}_{\text{3}}\text{O}\left(aq\right)+{\text{OH}}^{-}\left(aq\right)\Delta G°=79.9\text{kJ}$

For each of the following sets of concentrations, calculate ΔG at 25 °C and indicate whether the reaction is spontaneous in the forward or reverse direction:

1. (a) [H₃O⁺] = [OH^–] = 1.0 M
2. (b) [H₃O⁺] = [OH^–] = 1.0 × 10^–7M
3. (c) [H₃O⁺] = 1.0 × 10^–7M, [OH^–] = 1.0 × 10^–10M

   Are your results consistent with Le Châteliers principle? Use the thermodynamic data to calculate the equilibrium constant for the reaction.