In acid/base titration, knowing that it took 13.14 mL of 0.1016 M NaOH to reach the first endpoint of the titration, from this information, mmols of H3PO4 present in the sample is 1.335 mmols.
Here is the question: For the same titration above, it took 28.05 mL to reach the second endpoint. How many mmols of H2PO4- were present in the sample? Please help me solve this question. The answer is 0.18 mmols.