Question

A buffer solution contains 0.11 mol of acetic acid and 0.13 mol of sodium acetate in 1.00 L. What is the pH of this buffer?

Answer 1

Answer:

Henderson Hasselbalch equation: pH = pKa + log [salt]/[acid]

You need to know the pKa for acetic acid. Looking it up one finds it to be 4.76

(a). pH = 4.76 + log [0.13]/[0.10]

= 4.76 + 0.11

= 4.87

(b) KOH + CH3COOH =>H2O + CH3COOK so (acid)goes down and (salt)goes up. Assuming no change in volume, you have 0.10 mol acid - 0.02 mol = 0.08 mol acid and 0.13 mol salt + 0.02 mol = 0.15 mol salt

pH = 4.76 + log [0.15]/[0.08]

= 4.76 + 0.27

= 5.03