Final answer:
At a pH of 3, ammonium (NH4+) is the most abundant ionic species of ammonia (NH3) in solution because it is well below the pKa of 9.25, leading to the protonation of ammonia.
Step-by-step explanation:
At a pH of 3, the ionic species of ammonia (NH3) that is most abundant in solution is the conjugate acid ammonium (NH4+). As the pH is significantly below the pKa of ammonium, which is 9.25, the equilibrium lies towards the formation of NH4+. Ammonia is a weak base and its conjugate acid, ammonium, has a pKa value that determines the pH at which it can effectively act as a buffer.
In this case, since the pH of the solution is well below the pKa of ammonium, we can expect most of the ammonia to be protonated to form ammonium ions.
At a pH of 3, the solution is acidic. To determine the most abundant ionic species of ammonia in solution, we need to compare the pKa value of ammonium (NH4+) with the pH of the solution. The pKa of ammonium is 9.25. Since the pH of the solution is lower than the pKa, the ammonium ion (NH4+) will be more abundant than the ammonia (NH3) molecule in solution.