Final answer:
The titration curve for the titration of 25.0 mL of 0.125 M NH₃ with 0.0625 M HCl is determined by calculating the pH at each addition of HCl based on stoichiometry and using the Kb of NH₃.
Step-by-step explanation:
To calculate and construct a titration curve for the titration of 25.0 mL of 0.125 M NH₃ with varying volumes of 0.0625 M HCl, we have to determine the pH at each point. This involves using the provided Kb value for NH₃ and carrying out stoichiometric calculations.
Before the titration begins (0.0 mL of HCl), the pH is determined only by the NH₃ present. For the points after adding 30.0 mL, 50.0 mL, and 80.0 mL of HCl, we need to calculate the amount of NH₃ that reacts with the HCl and the amount of NH₄⁺ formed, which will then allow us to calculate the pH at each step. At the equivalence point of the titration, all NH₃ has reacted with HCl, and the solution will only contain NH₄⁺; its pH will be determined by the hydrolysis of NH₄⁺. Past the equivalence point, excess HCl will dominate the pH.
To precisely construct the titration curve, these pH values need to be plotted against the volumes of HCl added, giving us a graphical depiction of the titration process.