Assignment:
An unknown compound X, is thought to have a carboxyl group with a pka of 2.0 and another ionizable group with a pka between 5 and 8. When 75 ml of 0.1 M NaOH was added to 100 ml of a 0.1 m solution of X at pH 2.0, the pH increased to 6.72. Calculate the pKa of the second ionizable group of X.
Provide complete and step by step solution for the question and show calculations and use formulas.