0.001 moles of NH3 are added to 1 liter of pure water. The pKa of NH4 + = 9.25. Calculate the pH, [NH4 +], and [NH3] when 0.001 moles of HCl, a strong acid, are added to the solution? HCl is added from a concentrated stock solution, so the volume change is negligible.

To solve, you will need to use a charge balance expression in addition to equilibrium and mass balance expressions. You can also assume that the concentration of [H+] is negligible compared to other species in solution because NH3 is a base that will raise the pH of water that is initially at pH 7.0