Titration Curve : Ammonium with HCl?

Question

Given:
[HCl] = 0.100 M
Vol. of HCl need to reach Equivalence = 7.5 mL
Vol. of HCl needed to reach 1/2 Equivalence = 3.75 mL

Questions:

1. Determine the pKb and the Kb of the ammonium ion?

2. Calculate the concentration (M), of the aqueous ammonia solution?

Answer 1

1. Look at the titration curve, and go across from 3.75ml to the pH axis. That is the pKa, from which you can also calculate Ka. pKb = 14 - pKa.

2. Molarity of the NH3 = (7.5/vol NH3) x 0.1.

You did not state the volume of the NH3. It was probably 10ml.