determine the pKa2 value of H3PO4 using a procedure that is described below. Three pH measurements are made. You must calculate the predicted pKa at each measurement. Start with 10 mL of deionized/distilled water. Add 5.00 mL of 0.2 M HPO4. Add 2.00 mL 0.20 M HPO42, measure pH and calculate pKaz. 2- Add an additional 2.00 mL 0.20 M HPO4 (total added is 4.0 mL), measure pH and calculate pKaz. Add an additional 2.00 mL 0.20 M HPO4 (total added is 6.0 mL), measure pH and calculate pka2. Calculate pka2 average and calculate K2 average. Remember that for logarithmic values, you don't start counting significant figures until AFTER the decimal. For example, a pH of 7.34 has two significant figures, not three. HC (tra 1. If the pH after addition of 2.00 mL is 6.82, what is the pka2 to three significant figures? 2. If the pH after addition of an additional 2.00 mL (total is 4.00 mL) is 7.10, what is the pka2 to three significant figures? 3. If the pH after addition of an additional 2.00 mL (total is 6.00 mL) is 7.26, what is the pka2 to three significant figures? 4. pka2 average 5. Ka2 average.