"You can't just will the answer," she whispered. That was her problem. She had spent the whole year trying to memorise chemistry like it was history. Dates. Formulas. But chemistry wasn't a list. It was a story. Protons moving. Electrons trading places. Water molecules huddling around ions like concerned neighbours.
She calculated pH using the approximation for an amphiprotic: pH = (pKa1 + pKa2)/2. pKa1 = 1.81. pKa2 = 6.99. Average = 4.40. hsc chemistry 9 crack
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. "You can't just will the answer," she whispered
Mira put her head on the desk. The wood was cool. She could smell highlighter ink and her own exhausted sweat. It was a story
She wrote her answer in full sentences. Explained the hydrolysis. Compared Ka2 and Kb. Showed the approximation. Concluded pH = 4.40. Then she put her pen down.
Her father had knocked gently. "Mira? Everything okay?"