What is the pH of a buffer made by combining 181 mL of 0.34 M NaC₂H₃O₂ with 170 mL of 0.28 M HC₂H₃O₂? The K_a of acetic acid is 1.75 × 10^-5. A)4.88 B)4.64 C)5.93 D)4.83 E)5.38

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Quizplus · Accepted Answer

The pH of the buffer can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the acid. First, calculate the moles of NaCH3COO and HCH3COO: Moles of NaCH3COO = 0.34 M * 0.181 L = 0.06154 mol Moles of HCH3COO = 0.28 M * 0.170 L = 0.0476 mol The total volume of the solution = 181 mL + 170 mL = 351 mL = 0.351 L The concentration of NaCH3COO ([A-]) = 0.06154 mol / 0.351 L = 0.175 M The concentration of HCH3COO ([HA]) = 0.0476 mol / 0.351 L = 0.136 M pKa = -log(1.75 × 10^-5) = 4.76 pH = 4.76 + log(0.175/0.136) = 4.76 + log(1.287) = 4.76 + 0.11 = 4.87, which rounds to 4.88.

What Is the PH of a Buffer Made by Combining