If 20 mL of 0.10 M NaOH is added to 30 mL of 0.20 M HC₂H₃O₂,what is the pH of the resulting solution at 25°C? K_a for HC₂H₃O₂ is 1.8 × 10^-5 at 25°C. A)10.2 B)4.3 C)5.0 D)2.7 E)4.4

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The solution is a buffer after the reaction between NaOH and HC2H3O2. Use the Henderson-Hasselbalch equation to find the pH: pH = pKa + log([A-]/[HA]). After the reaction, [A-] = 0.002 mol and [HA] = 0.004 mol, so pH = 4.74 + log(0.002/0.004) = 4.4.

If 20 ML of 0