The pH is defined for our present purposes as

pH = - log₁₀ ([H⁺]/c°).

Find the pH of a solution formed from 0.075 mol of NH₃ and enough water to make 1.00 l of solution. The ionization that occurs is

NH₃ + H₂O ⇋ NH⁺₄ + OH^-.

The equilibrium expression in terms of molar concentrations is

where x(H₂O) represents the mole fraction of water, which is customarily used instead of its molar concentration. Since the mole fraction of the solvent in a dilute solution is nearly equal to unity, we can use the approximate version of the equation. The base ionization constant of NH₃, denoted by K_b, equals 1.80 × 10^-5 at 25^°C.

Transcribed Image Text:

([NH1/c°) ([OH 1/c°) x (H2O)([NH3]/c°) (INH]/c°)([OH-]/c°) ([NH3]/c°)