Final answer:
An accurate calculation of the pH change cannot be provided due to incomplete information about the pKa value for the buffer system and the ambiguity surrounding 'hal'.
Step-by-step explanation:
We need to consider the buffer capacity and the Henderson-Hasselbalch equation. Unfortunately, the details required to perform this calculation are incomplete because the pKa for the NH4+/NH3 buffer system is not provided, and the exact nature of the added 'hal' is ambiguous, presumably meaning hydrohalic acid.
Assuming the pKa of NH4+ is approximately 9.25 (a typical value for ammonia), and the strong acid added is HCl, the acid would react completely with the NH3 to form NH4+. The following equation can be applied: HCl + NH3 -> NH4+ + Cl-
Due to the stoichiometry of the reaction, 0.003 moles HCl will react with 0.003 moles NH3, reducing the amount of NH3 and increasing the amount of NH4+. The Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), can be used to find the new pH.