A 300.0 mL buffer solution is 0.260 M in acetic acid and 0.260 M in sodium aceta
ID: 506414 • Letter: A
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