Actual experimental concentrations: Acetic acid concentration: 1.060 M Sodium ac

Question

Actual experimental concentrations:

Acetic acid concentration: 1.060 M

Sodium acetate concentration: 1.068 M

Undiluted buffer solution is prepared by mixing 100 mL of 1.060 M acetic acid with 100 of 1.068 M sodium acetate solution

4. Calculate the volume of 3 M NaOH needed to change the pH of 75 mL of the undiluted buffer solution by one pH unit (buffer capacity), use actual experimental concentrations. Note (here is how to solve this question): As the base is added the equilibrium below shifts to the right and the moles of CH3COOH decreases and the moles of CH3COO increases. Initial moles of CH3COOH = 1 M x x 0.075 L= 0.0375 moles Initial moles of CH3COO 1Mx00 x0.075L 0.0375 moles Let x = number of moles of base added When OH is added the moles of CH3COOH will decrease by 0.0375 moles - x moles When OH is added the moles of CH;COO will increase by 0.0375 moles +x moles When NaOH is added the pH will increase, therefore we can use a pH value of pH = (pKa + 1), and use the following equation to answer the question. [0.0375 +x] [0.0375 -x) A ] pH = pKa + log 5.75 = 4.75 + log

Explanation / Answer

b = 2.303 Cacid Cconjugate base / (Cacid + Cconjugate base)

b = 2.303 * 1.060 * 1.068/(1.060 + 1.068) = 1.225 M

b = dCbase/dpH

1.225 = dCbase/1

dCbase = 1.225

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