Posted by ibob on .
What is the pH of the solution created by combining 2.80 mL of the 0.10 M NaOH(aq) with 8.00 mL of the 0.10 M HC2H3O2(aq)?
I got 1.3. is that correct?
STEP 1: STOICHIOMETRY to find moles C2H3O2- formed and HC2H3O2 remaining. All NaOH was used up, so that's how many moles reacted with the HC2H3O2 and also how many moles C2H3O2- formed.
STEP 2: EQUILIBRIUM of HC2H3O2 with H+ and C2H3O2-. Change the moles of HC2H3O2 and C2H3O2- into molarities by dividing by the TOTAL VOLUME (0.00280 L + .008L = .01080 L) and plug those into the equilibrium equation. (The value of K for HC2H3O2, or acetic acid, is 1.8 X 10 ^-5)
STEP 3: SOLVE FOR pH
SUMMARY: NaOH is a strong base - Stoichiometry
Acetic acid is a weak acid - Equilibrium
Use the equilibrium equation to solve for [H+], then the pH
No, 1.3 is not the answer. Follows Bill's instructions OR use the Henderson-Hasselbalch equation.