Compare Ka2 (1.02×10⁻⁷) to Kb (6.49×10⁻¹³). Ka2 is much larger . So the HSO₃⁻ acts as a weak acid. The solution is slightly acidic. Of course. The pH at equivalence is below 7. Not neutral. That was the trap.
Mira looked at the clock. 12:31 AM. She smiled—a small, tired, real smile. Then she closed the 9-pack, placed it on top of her textbook, and went to sleep. hsc chemistry 9 crack
She had not avoided the cracks. She had crawled inside them, felt the rough edges, and found that the light still got through. Compare Ka2 (1
She wrote: At equivalence point for first proton: species present = HSO₃⁻. This hydrolyses in water. Two equilibria: HSO₃⁻ + H₂O ⇌ H₂SO₃ + OH⁻ (Kb1) AND HSO₃⁻ ⇌ H⁺ + SO₃²⁻ (Ka2). Since Ka2 > Kb1, solution is acidic? No—check values. The solution is slightly acidic
Her father had knocked gently. "Mira? Everything okay?"