Question
The dissolution of ammonia gas in water does not obey Henry's law. On dissolving, a major portion o fammonia, molecules unite with H2O to form NH4OH molecules. NH4OH again dissociates into NH+4 and OH− ions. In solution therefore, we have NH3 molecules, NH4OH molecules and NH+4 ions and the following equilibrium exist:
NH3(g) (pressure P and concentration c) Initially ⇌NH3(l)+H2O⇌NH4OH⇌NH+4+OH−
Let c1 mol/L of NH3 pass in liquid state which on dissolution in water froms c2 mol/L of NH4OH. The solution contains c3 mol/L of NH+4 ions. The dissociation constant of NH4OH can be given as: