A 300.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium aceta

Question

A 300.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium acetate. A) What is the initial pH of this solution? B) What is the pH after addition of 0.0150 mol of HCl? C) What is the pH after addition of 0.0150 mol of NaOH?
All to two decimal places. A 300.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium acetate. A) What is the initial pH of this solution? B) What is the pH after addition of 0.0150 mol of HCl? C) What is the pH after addition of 0.0150 mol of NaOH?
All to two decimal places. A) What is the initial pH of this solution? B) What is the pH after addition of 0.0150 mol of HCl? C) What is the pH after addition of 0.0150 mol of NaOH?
All to two decimal places.

Explanation / Answer

moles of acetic acid = 300 x 0.260 / 1000 = 0.078

moles of sodium acetate = 300 x 0.260 / 1000 = 0.078

a)

pH = pKa + log [sodium acetate / acetic acid]

pH = 4.74 + log (0.078 / 0.078)

pH = 4.74

B)

C = 0.0150

pH = pKa + log [sodium acetate - C / acetic acid + C]

pH = 4.74 + log (0.078 -0.015 / 0.078 + 0.0150)

pH = 4.57

C )

pH = pKa + log [sodium acetate + C / acetic acid - C]

pH = 4.74 + log (0.078 + 0.015 / 0.078 - 0.0150)

pH = 4.91

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