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TEEN Chemistry QUESTION #1107
Question 1
For phosphoric acid ionizing in three steps with \(K_{a1}, K_{a2}, K_{a3}\) and overall K. Which statements are true? A. \(\log K = \log K_{a1}+\log K_{a2}+\log K_{a3}\). B. H\(_3\)PO\(_4\) is stronger acid than H\(_2\)PO\(_4^-\) and HPO\(_4^{2-}\). C. \(K_{a1}>K_{a2}>K_{a3}\). D. \(K_{a1}=\frac{K_{a3}+K_{a2}}{2}\)
  • B, C and D only
  • A, B and C only✔️
  • A and B only
  • A and C only
Correct Answer Explanation
A: Overall K = K\(_{a1}\)\(\times\)K\(_{a2}\)\(\times\)K\(_{a3}\), so \(\log K=\log K_{a1}+\log K_{a2}+\log K_{a3}\) ✓. B: Each successive ionization is from a more negatively charged species → harder to remove H\(^+\) → H\(_3\)PO\(_4\) is strongest ✓. C: \(K_{a1}>K_{a2}>K_{a3}\) because successive ionizations from more negative species ✓. D: No such relationship exists — D is false. Correct: A, B, C = option (2).