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A buffer solution is prepared by mixing 15.0 mL of 2.20 M Acetic Acid and 30.0 mL of 1.55 M NaC2H3O2. ?
Determine the pH of the solution after the addition of 0.01 moles NaOH (assume there is no change in volume when the NaOH is added).
1 Answer
- hcbiochemLv 711 hours ago
Moles HAc = 0.0150 L X 2.20 mol/L = 0.0330 mol HAc
moles Ac- = 0.030 L X 1.55 mol/L = 0.0465
Adding 0.01 mol NaOH will quantitatively neutralize 0.0100 mol HAc forming an additional 0.0100 mol Ac-. So, after the addition:
moles HAc = 0.0230
moles Ac- = 0.0565
pH = pKa + log [Ac-]/[HAc]
pH = 4.74 + log (0.0565/0.0230)
pH = 5.13
(Note: I used actual moles of Ac- and HAc in the calculation rather than using molarities. This is find to do since a ratio of moles will equal the ratio of molarities.)