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A student was given a 0.15 M solution of an unknown diprotic acid H2A and asked to determine the Ka1 and Ka2 values for the diprotic acid. The student titrated 44.4 mL of the 0.15 M H2A with 0.15 M KOH. After 22.2 mL of KOH was added, the pH of the resulting solution was 6.37. After 44.4 mL of KOH was added, the pH of the resulting solution was 8.34. What is the value of Ka2 for the diprotic acid when ka1 is 4.2e-7?