The equilibrium constant for the reaction of hydrochloric acid and ammonia is 1.8 × 10⁹ (page 726). Confirm this value.

Data given on Page 726

The net ionic equation for the reaction of the strong acid HCl and the weak base  NH₃ is
The hydronium ion, H₃O⁺, is a much stronger acid than NH₄⁺ (K_a = 5.6 × 10⁻¹⁰), and NH₃ is a stronger base (K_b = 1.8 × 10⁻⁵) than H₂O. Therefore, the reaction is predicted to proceed to the right and to reach completion. After mixing equal amounts of HCl and NH₃, the solution contains the salt ammonium chloride, NH₄Cl. The Cl⁻ ion has no effect on the solution pH (Tables 16.2 and 16.3). However, the NH₄⁺ ion is the conjugate acid of the weak base NH₃, so the solution at the conclusion of the reaction is acidic.

Transcribed Image Text:

H30+ (aq) + NH3(aq) → H₂O(l) + NH4+ (aq)