Having respectively equilibrium constants equal to K1 = 10 -14 and K2 = 5.75 * 10 -10 and starting concentrations of H2O = 1.0 and NH3 = 0.1 . Performance tested on a case study for chempy documentation example. To skew the times in favor of vpasolve and chempy, we removed overhead time for defining symbolic variables and system of equations.