Answer:
a. 5.10.
b. 4.35.
c. 5.10.
d. 4.35.
Explanation:
<u><em>a. 0.10 M acetic acid/0.25 M sodium acetate </em></u>
For acidic buffer:
∵ pH = pKa + log [salt]/[Acid]
∴ pH = - log(Ka) + log [salt]/[Acid]
Ka for acetic acid = 1.8 x 10⁻⁵.
∴ pH = - log(1.8 x 10⁻⁵) + log(0.25)/(0.10)
∴ pH = 4.744 + 0.34 = 5.084 ≅ 5.10.
<u><em>b. 0.25 M acetic acid/0.10 M sodium acetate</em></u>
For acidic buffer:
∵ pH = pKa + log [salt]/[Acid]
∴ pH = - log(Ka) + log [salt]/[Acid]
Ka for acetic acid = 1.8 x 10⁻⁵.
∴ pH = - log(1.8 x 10⁻⁵) + log(0.10)/(0.25)
∴ pH = 4.744 - 0.34 = 4.346 ≅ 4.35.
<u><em>c. 0.080 M acetic acid/0.20 M sodium acetate</em></u>
For acidic buffer:
∵ pH = pKa + log [salt]/[Acid]
∴ pH = - log(Ka) + log [salt]/[Acid]
Ka for acetic acid = 1.8 x 10⁻⁵.
∴ pH = - log(1.8 x 10⁻⁵) + log(0.20)/(0.08)
∴ pH = 4.744 + 0.34 = 5.084 ≅ 5.10.
<u><em></em></u>
<u><em>d. 0.20 M acetic acid/0.080 M sodium acetate</em></u>
For acidic buffer:
∵ pH = pKa + log [salt]/[Acid]
∴ pH = - log(Ka) + log [salt]/[Acid]
Ka for acetic acid = 1.8 x 10⁻⁵.
∴ pH = - log(1.8 x 10⁻⁵) + log(0.08)/(0.20)
∴ pH = 4.744 - 0.34 = 4.346 ≅ 4.35.
