Question

How much 5.6 M NaOH must be added to 490 mL of a buffer that is .190 M acetic acid and .025 M sodium acetate to raise the pH to 5.75?

Answer 1

pH = pka + log(salt+NaOH/acid-NaOH)

No of mol of Salt = 0.49*0.025 = 0.01225 mol

No of mol of ACID = 0.49*0.19 = 0.0931 mol

5.75 = 4.74 + log((0.01225+x)/(0.0931-x))

x = No of mol of NaOH = 0.084 mol

Volume of NaOH = 0.084/5.6 = 0.015 L

= 15 ml