Digital ACT Science Practice Question #1862

Between 25 drops and 60 drops of HCl, the phosphate buffer experienced a rapid drop in pH from 6.95 to 4.20 because: Experiment Context (Acid-Base Buffering Capacity of Phosphate Buffer): Biochemists prepared 100 mL of 0.10 M phosphate buffer (H2PO4- / HPO4(2-), pH 7.20) and 100 mL of unbuffered pure water (pH 7.00), adding 1.0 M HCl dropwise while recording pH: Table 36: - 0 drops HCl: Phosphate Buffer pH = 7.20; Pure Water pH = 7.00 - 2 drops HCl: Phosphate Buffer pH = 7.19; Pure Water pH = 3.85 - 5 drops HCl: Phosphate Buffer pH = 7.16; Pure Water pH = 3.10 - 10 drops HCl: Phosphate Buffer pH = 7.10; Pure Water pH = 2.45 - 25 drops HCl: Phosphate Buffer pH = 6.95; Pure Water pH = 1.90 - 60 drops HCl: Phosphate Buffer pH = 4.20; Pure Water pH = 1.40