Question

1. A 40.0 mL sample of 0.205 M NH3(aq) is titrated with 0.250 M HBr(aq) at 25 oC. The pKb for NH3 is 4.74 at 25 oC.
(a) (4 Marks) Using all correct symbols and arrows, write the complete balanced chemical equation and net ionic equation for the neutralization reaction upon which this titration is based.
(b) (4 Marks) What is the pH of the initial solution of NH3(aq)? Write the appropriate balanced equilibrium reaction that governs the pH of the solution. Show the appropriate ICE table and all relevant calculations.
2. For each of the following stages of the titration described above (in question 1), calculate and report the pH, [NH3] and [NH4+]. For each stage, write the ice table and equilibrium reaction that governs the pH of the solution. Show all relevant calculations and ice tables, and explain any approximations used.
(Note: To assist with the grading, at the end of the full solution, please include a summary stating:
pH = XXX, [NH3] = XXX, and [NH4+] = XXX, with your calculated values).
(a) (5 Marks) After the addition of 20.0 mL of HBr(aq) solution.
(b) (5 Marks) At the equivalence point.