I believe you were already given one of the reaction "equation" here:http://www.chemicalforums.com/index.php?topic=23518.0
I suggest you:
1. calculate the [H+] present from the titration data in the "test" section of the problem.
this gives you the following information pH (from your measurement),Pka (listed) and [H+].
Check you textbook (in the chapter on pH) and find an equation which requires all of the above (and contains an unknown quantity).
2. Calculate the value of the unknown.
3. Repeat step 1 for the blank.
This should supply you with all the information you need to answer the questions.