If 20 mL of 0.10 M NaOH is added to 35 mL of 0.20 M HC₂H₃O₂,what is the pH of the resulting solution at 25°C? K_a for HC₂H₃O₂ is 1.8 $\times$ 10^-5 at 25°C. A) 10.0 B) 4.2 C) 5.1 D) 2.7 E) 4.3

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The solution is a buffer after the reaction between NaOH and HC2H3O2. Using the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), where [A-] and [HA] are the concentrations of acetate and acetic acid, respectively. After the reaction, [A-] = 0.002 mol and [HA] = 0.005 mol, giving pH ≈ 4.3.

If 20 ML of 0 ×\times× 10-5 at 25°C

If 20 ML of 0 $\times$ 10^-5 at 25°C