When a strong base titrant (e.g. NaOH) is added, the following reactions occur: (iv) H2A(aq) + OH(aq) -> H2O(l) + HA-(aq) (v) HA-(aq) + OH(aq) -> H2O(l) + A2-(aq) Note: single arrow to the right rather than double arrow means the reactions go to completion 4. Which region (A,B,C,D,E, or F) is where the titration begins and H2A is the predominant species in solution ? ____________ 5. Which reaction (iv or v) dominates at low pH values? _____________ 6. Halfway through which region (A,B,C,D,E, or F) is where the pH = pKa1 ? ____________
B. When a strong base titrant (e.g. NaOH) is added, the following reactions occur:
(iv) H2A(aq) + OH(aq) -> H2O(l) + HA-(aq)
(v) HA-(aq) + OH(aq) -> H2O(l) + A2-(aq)
Note: single arrow to the right rather than double arrow means the reactions go to completion
4. Which region (A,B,C,D,E, or F) is where the titration begins and H2A is the predominant species in solution ? ____________
5. Which reaction (iv or v) dominates at low pH values? _____________
6. Halfway through which region (A,B,C,D,E, or F) is where the pH = pKa1 ? ____________
7. Explain your answer to #6 in terms of the Henderson-Hasselbalch equation.
8. Which species (H2A, HA-, or A2-) predominates at "C", the equivalence point 1 ?
9. During the titration, which region (A,B,C,D,E, or F) on the curve represents the first buffer region? _____________ ? Second buffer region _____________ ?
10. Halfway through the second buffer (region "D"), the pH = pKa2. What is the value of pKb1 ? (Use the relationship that pKa2 + pKb1 = 14 )
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