Chemistry
posted by Elaine .
a 25.0 mL sample of .050 M solution of aqueous trimethylamine is titrated with a .063 M solution of HCl. calculate pH the solution after 10.0 mL, 20.0 mL, 30.0 mL of acid have been added. pKb of (CH3)_3_N= 4.19 at 25 degrees C

First determine where the equivalence point is so you will know where you are on the titration curve with each of thes additions.
mL x M = mL x M
25.0 x 0.05 = mL x 0.063
mL = about 19 or so.
Therefore, 10 mL will be before the e.p. and you will have some base and some of its conjugate. Use the HendersonHasselbalch equation.
b. 20 mL will be just after the e.p. So you will have an excess of 20 mLmL for e.p. That will be an excess of HCl
c. 30 mL is same as part b.